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DEPARTMENT OF THE ARMY TECHNICAL MANUAL
SOUND
LOCATING
SET GR-6-A
DEPARTMENT OF THE ARMY . JUNE 1951
DEPARTMENT OF THE ARMY TECHNICAL MANUAL
TM 11-2552A
SOUND
LOCATING
SET GR-6-A
DEPARTMENT OF THE ARMY JUNE 1951
United States Gcn-ernmenl Printing Office
Washington: 1951
DEPARTMENT OF THE ARMY
Washington 25, d. c, i June 1951
TM 11-2552A is published for the information and guidance of all con
cerned.
[AG413.6 (17 May 51)]
By order of the Secretary of the Army:
Official: J. LAWTON COLLINS
WM. E. BERGIN Chief of Staff, United States Army
Major General, USA
Acting The Adjutant General
Distribution :
Tech Svc (2) except 11 (65) ; Arm & Svc Bd (1) ; AFF Bd (ea Svc Test
Sec) (1) ; AFF (5) : AA Comd (2) ; OS Maj Comd (5) : Base Comd
(5) ; MDW (5) ; Log Comd (5) ; A (20) ; CHQ (2) ; FC (2) ; Sch
(2) except 11 (25) ; Gen Dep (2) ; Dep 11 (20) except Sig Sec, Gen
Dep (10) ; Tng Div (2) ; PE (10), OSD (2) ; Lab 11 (5) ; 4th & 5th
Ech Maint Shops 11 (3) ; Two (2) copies to each of the following
T/O & E's: 11-107; 11-127; 11-500 CA, CB, CC, CD; 11-587; 11-
592 ; 11-597 ; SPECIAL DISTRIBUTION.
For explanation of distribution formula, see SR 310-90-1.
ii
CONTENTS
CHAPTER 1. INTRODUCTION. Paragraph. Page
Section I. General 1-2 1
//. Description and data 3-17 1
CHAPTER 2. OPERATING INSTRUCTIONS.
Section I. Service upon receipt of equipment 18-19 14
//. Controls and their use 20-21 14
///. Operation under usual conditions 22-27 17
IV. Operation under unusual conditions 28-31 24
V. Computing azimuth and range 32-37 25
CHAPTER 3. MAINTENANCE INSTRUCTIONS.
Section I. Preventive maintenance services 38-40 33
//. Lubrication and preservation 41-42 34
CHAPTER 4. FIELD MAINTENANCE INSTRUCTIONS.
Section I. General 43-44 36
//. Theory of operation 45-51 36
///. Prerepair procedures 52-54 42
IV. Trouble location 55-59 44
V. Repairs 60-61 48
CHAPTER 5. SHIPMENT AND LIMITED STORAGE AND
DEMOLITION TO PREVENT ENEMY USE.
Section I. Shipment and limited storage 62-63 52
//. Demolition to .prevent enemy use 64-65 52
APPENDIX I. REFERENCES 55
II. IDENTIFICATION TABLE OF PARTS 58
INDEX 64
r
WARNING
A potential of
600 VOLTS
is used in the operation of
this equipment.
DEATH ON CONTACT
may result if personnel fail to
observe safety precautions.
Be careful not to contact high-voltage output connections of the dyna-
motors and of the cathode-ray tube when checking or trouble shooting this
equipment. When working inside the equipment after the power has been
turned off, always ground every part before touching it.
DANGEROUS VOLTAGES
exist in Recorder BC-1323-A.
First Aid for
Electric Shock j
RESCUE.
In case of electric shock, shut off Iho high voltage
at oncp and ground the circuits. If the high voltage
cannot lie turned off without delay, free the victim
from contact with the live conductor as promptly as
possible. Avoid direct contact with either the live
conductor or the victim's hody. Use a dry hoard, dry
clothing, or other nonconductor to free the victim.
An ax may be used to cut the high voltage wire. Use
extreme caution to avoid the resulting electric flash.
SYMPTOMS.
d. Breathing stops abruptly in electric shock if
the current passes through the breathing center at
the base of the brain. If the shock has not been too
severe, the breath center recovers after a while and
normal breathing is resumed, provided that a suf
ficient supply of air has been furnished meanwhile
by artificial respiration.
b. The victim is usually very white or blue. The
pulse is very weak or entirely absent and uncon
sciousness is complete. Hums are usually present.
The victim's body may become rigid or stiff in a
very few minutes. This condition is due to the action
of electricity and is not to be considered rigor mor
tis. Artificial respiration must still be given, as sev
eral such cases are reported to have recovered. The
ordinary and general tests for death should never
be accepted.
TREATMENT.
*>. Start artificial respiration immediately. At the
same time send for a medical officer, if assistance is
available. Do not leave the victim unattended. Per
form artificial respiration at the scene of the acci
dent, unless the victim's or operator's life is endan
gered from such action. In this rase only, remove
the victim to another location, but no farther than
is necessary for safety. If the new location is more
than a few feet away, artificial respiration should
he given while the victim is being moved. If the
method of transportation prohibits the use of the
Shaeffer prone pressure method, other methods of
resuscitation may be used. Pressure may be exerted
on the front of the victim's diaphragm, or the direct
mouth to mouth method may be used. Artificial res
piration, once started, must bo continued, without
loss of rhythm.
b. I„iy the victim in a prone position, one arm
extended directly overhead, and the other arm bent
at the elbow so that the back of the hand supports
the head. The face should be turned away from the
bent elbow so that the nose and mouth are free for
breathing.
c. open the victim's mouth and remove any for
eign bodies, such as false teeth, chewing gum, or
tobacco. The mouth should remain open, with the
tongue extended. Do not permit the victim to draw
his tongue back into his mouth or throat.
d. If an assistant is available during resuscita
tion, he should loosen any tight clothing to permit
free circulation of blood and to prevent restriction
of breathing He should see that the victim is kept
warm, by applying blankets or other covering, or
by applying hot rocks or bricks wrapped in cloth or
paper to prevent injury to the victim. The assistant
should also be ever watchful to see that the victim
does not swallow his tongue. He should continually
wipe from the victim's mouth any frothy mucus or
saliva that may collect and interfere with respira
tion.
e. The resuscitating operator should straddle the
victim's thighs, or one log, in such manner that:
(/) the operator's arms and thighs will be ver
tical while applying pressure on the small of the vic
tim's back;
(2) the operator's fingers are in a natural po
sition on the victim's back with the little finger lying
on the last rib;
(.1) the heels of the hands rest on either side
of the spine as far apart as convenient without al
lowing the hands to slip off the victim;
(1) the operator's elbows are straight and
locked.
f- The resuscitation procedure is as follows:
(/) Kxert downward pressure, not exceeding
GO pounds, for 1 second.
(2) Swing back, suddenly releasing pressure,
and sit on the heels.
IX) After 2 seconds rest, swing foi-ward again,
positioning the hands exactly as before, and apply
pressure for another second.
g. The forward swing, positioning of the hands,
and the downward pressure should be accomplished
in one continuous motion, which requires 1 second.
The release and backward swing require 1 second.
The addition of the 2-second rest makes a total of 4
TLI5338- D
Vi
seconds for a complete cycle. Until the operator is
thoroughly familiar with the correct cadence of the
cycle, he should count the seconds aloud, speaking
distinctly and counting evenly in thousands. Exam
ple: one thousand and one, one thousand and two,
etc.
h. Artificial respiration should be continued until
the victim regains normal breathing or is pro
nounced dead by a medical officer. Since it may be
necessary to continue resuscitation for several
hours, relief operators should be used if available.
RELIEVING OPERATOR.
The relief operator kneels beside the operator and
follows him through several complete cycles. When
the relief operator is sure he has the correct rhythm,
he places his hands on the operator's hands without
applying pressure. This indicates that he is ready to
take over. On the backward swing, the operator
moves and the relief operator takes his position.
The relieved operator follows through several com
plete cycles to be sure that the new operator has
the correct rhythm. He remains alert to take over
instantly if the new operator falters or hesitates on
the cycle.
STIMULANTS.
a. If an inhalant stimulant is used, such as aro
matic spirits of ammonia, the individual administer
ing the stimulant should first test it himself to see
how close he can hold the inhalant to his own nos
tril for comfortable breathing. Be sure that the in
halant is not held any closer to the victim's nostrils,
and then for only 1 or 2 seconds every minute.
b. After the victim has regained consciousness,
he may be given hot coffee, hot tea, or a glass of
water containing ',i teaspoon of aromatic spirits of
ammonia. Do not girc any liquids to an unconscious
victim.
CAUTIONS.
a. After the victim revives, keep him LYING
QUIETLY. Any injury a person may have received
may cause a condition of shock. Shock is present if
the victim is pale and has a cold sweat, his pulse is
weak and rapid, and his breathing is short and
gasping.
b. Keep the victim lying flat on his back, with
his head lower than the rest of his body and his
hips elevated. Be sure that there is no tight clothing
to restrict the free circulation of blood or hinder
natural breathing. Keep him warm and quiet.
c. A resuscitated victim must be watched care
fully as he may suddenly stop breathing. Never
leave a resuscitated person alone until it is CER
TAIN that he is fully conscious and breathing nor
mally.
Til 531*4
Vll
CHAPTER 1
INTRODUCTION
Section I. GENERAL
1 . Scope
a. These instructions are published for the
information and guidance of the personnel to
whom the equipment is issued. Then contain
information on the operation, organizational
maintenance, and field maintenance of the
equipment as well as a discussion of the theory
of operation. They apply only to Sound Locat
ing Set GR-6-A.
6. Appendix I contains a list of current refer
ences, including supply catalogs, technical man
uals, and other available publications applicable
to the equipment. Appendix II contains an iden
tification table of parts.
2. Forms and Records
The following forms will be used for report
ing unsatisfactory conditions of Army equip
ment and in performing preventive mainte
nance :
a. DD Form 6, Report of Damaged or Im
proper Shipment, will be filled out and for
warded as prescribed in SR 745-45-5.
b. DA AGO Form 468, Unsatisfactory Equip
ment Report, will be filled out and forwarded to
the Office of the Chief Signal Officer, as pre
scribed in SR 700^5-5.
c. DA AGO Form 419, Preventive Mainte
nance Checklist for Signal Corps Equipment,
will be prepared in accordance with instructions
on the back of the form.
d. Use other forms and records as authorized.
Section II. DESCRIPTION AND DATA
3. General
Sound Locating Set GR-6-A is a 6-volt, d-c
(direct-current) powered device used to deter
mine the range and azimuth of small arms fire.
The sound of a muzzle blast is picked up by an
array of three, specially placed microphones
whose output is fed to a recorder (fig. 1). The
recording is made on steel tape and played back
to operating personnel who determine the point
of origin of the enemy gunfire. The sound locat
ing set includes appropriate telephone equip
ment, a radio transmitter and receiver, a gaso
line-engine-driven generator for charging the
supplied lead-acid-type storage batteries, and
other allied equipment and accessories required
to operate and maintain the equipment (fig. 2) .
4. Technical Characteristics
Input volts 5.6 to 6.3 v dc.
Input power 4.2 amp (amperes) ; 30 to
33 w.
Number of amplifier
channels 3; each using three type
9001 tubes.
Frequency range
(amplifier) 60 to 300 cycles, recording
and reproducing.
Frequency response . . Response of the three chan
nels within ± 2 db (deci
bels).
Phase matching Relative differences in elec
trical phase between any
two channels within 0.2
milliseconds.
Operating range .... Nominal range 2,000 to
4,000 yards.
1
BAG BG-I60-A
Figure 2. Sound Locating Set GR-6-A, major components.
5. Table of Components
Equipment
Recorder BC-1323-A and Bag BG-182-A
Bag BG-160-A, each containing the following:
4 Microphone T-56 _
4 Microphone Shelter M 413
2 legs for recorder.
1 Cord CD-1238-A.
3 Cord CD-1239.
1 Cord CD-1240.
1 Cord CD-1444.
1 Chain Kit MC-692.
1 drill, star.
1 Hammer TL-332/U.
Case C8-161, each containing the following:
1 Handset TS-10-P.
1 Headset HS-30-U complete with Cord CD-874.
1 Computor M-114 in Case CS 148.
1 Cord CD-1446.
3 Marker MC-693.
1 Plotting Board M-10 (in Case M-72).
1 Compass M-2 in Case.
1 Holder M-167-A.
1 notebook.
6 pencils.
1 funnel.
4 tubes, type 9001.
1 tube, type 6AK6.
1 tube, type 2AP1-A.
1 rectifier (selenium).
3 lamp, incandescent, 6.3 v.
5 steel (recording) tape (rolls)
Dimensions (in.;
Length Height Width Dian
30 8
12 9
SH'2
6
18
Weight(lb)
4Vi
33
16
35
1
11
2
EquipmentDimensions (in.)
Length Height I Width Diam
Weight(lb.)
12 fuses, 6 amp, 250 v.
11 fuses, Y% amp, 250 v.
4 battery caps for BB-221/U.
4 battery caps for BB-54.
Reel Equipment CE-11
Bag BG-44 (fig. 10) including the following:
1 typewriter brush.
1 camel 's-hair brush.
1 soldering iron.
1 Pliers TL-304/U.
1 pair needle-nosed pliers.
1 Pliers TL-103.
3 Flashlight TL-122-D.
1 screw driver, 4-in. offset.
1 screw driver, 6-in. offset.
1 screw driver, 8 in.
1 Multimeter TS-297/U.
1 pair tweezers, 4 in.
1 sandpaper, No. 00, 6 strips.
1 carbon tretrachloride, 8-oz can.
1 tube cement.
2 lubricating oil, 4-oz can.
1 can soldering paste.
1 solder, 1-lb spool.
1 insulating tubing, 2 ft long.
1 Tape TL-83.
1 Tape TL-94.
3 Holder M-167-A, clipboard.
Battery Box CH-291
Battery Box CH-318
20%
12
12%
63-2
H34
5^ 4Ji
18
Note. This list is for general information only. See appropriate publications for information pertaining to requisitioning of spare parts.
6. Equipment Required but Not Supplied
Quantity Name Remarks
1 Power Unit PE-210 450 w, 30 amp at 15 v.
Battery BA-30... 1.5 v.
3 Radio Set SCR-300-A
36 Battery BB-54 2 v.
12 Battery BB-221/U 6 v.
Erasers..._
3 Rule, 6 in
7. Packaging Data
Sound Locating Set GR-6-A is export-packed in seven wooden boxes. The table below lists the
contents and dimensions of each box.
Box Item No. ofpackages
Dimensions (in.)Volume(cu ft)No.
Length Width Height
1/7 Recorder BC-1323-A 1 36 15 12 3.8
2/7 Recorder BC-1323-A 1 36 15 12 3.8
3/7 Recorder BC-1323-A 1 36 15 12 3.8
4/7 Bag BG-160-A with contents 3 46 40 15 16.0
5/7 Case CS-161 with contents 3 35 20 14 5.6
6/7 Consolidated packages 2 29 24 18 7.3
7/7 12 ea Battery Box CH-291 2 37 31 28. 18.5
and
6 ea. Batterv Box CH-318
3
8. Recorder BC-1 323-A
(figs. 3, 4, and 5)
a. General. Recorder BC-1323-A consists
of three microphone amplifiers, a headset ampli-
hand. The following controls are mounted on
the front panel: a main control lever (S1), a
play-back lever (S2) , a volume control with sev
en steps of attenuation, a viewing tube to permit
the operator to see the pattern on the oscillo-
TM2552A-
Figure S. Recorder BC-1S2S-A, in viewing position.
fier, a bias and erase oscillator, a cathode-ray
tube, and a recorder mechanism. Three record
ers are supplied with the GR-6-A, two in use
and one spare.
b. Front Panel. Figure 3 shows the record
er in the operating position. On the front panel
(fig. 14), at the extreme right, is a scanning
wheel for controlling the tape movement by
scope, two counter adjustment knobs and their
respective counters, a push-button switch (S3),
and an access cover lock.
c. Side Panel (figs. 4 and 15) . On the record
er side panel are two female connectors (J1
and J4) marked MICROPHONE and STOP
SWITCH; two male connectors (P1 and P2)
marked RADIO and 6V; two Binding Posts
4
TM-175 marked LINE, two terminal posts
marked HAND SET, a double-pole, double-
throw toggle switch (S4) marked RADIO—
SURVEY—OFF ; a toggle switch (S7) for pow
er marked ON-OFF; two phone jacks (J2 and
J3) marked RADIO HANDSET; a phone jack
(J5) marked PHONES; three fuses (F1, F2,
and F3) inclosed by a cover marked SERVICE
FUSES; and two potentiometer control knobs
marked FOCUS and INTENSITY.
1 0. Bag BG-1 60-A and Contents
Three Bags BG-160-A (fig. 6) are supplied
with each sound locating set. Each bag contains
the following components :
a. Microphone T-56. Four magnetic-type
microphones are packed in each Bag BG-160-A.
Each microphone has a receptacle for connector
P103 on Cord CD-1238-A. A stake is provided
for ground insertion.
TM 2552A-4
Figure 4. Recorder BC-1323-A, side controls exposed for operation.
d. Rear Panel. The following parts are
mounted on the recorder rear panel (figs. 5 and
16) : a relay (O-1), a clip which holds the
Allen-head and Bristol wrenches, a tube-pin
straightener, and three spare fuses.
9. Bag BG-182-A
Three rubberized fabric Bags BG-182-A (fig.
2) are supplied with each Sound Locating Set
GR-6-A. They provide waterproof protection
during transportation and storage of Record
ers BC-1323-A.
b. Microphone Shelter M-413. The micro
phone shelters are wind screens made of two
layers of cloth, circular in shape and approxi
mately 33 inches in diameter. A link chain, cov
ered with rubber tubing and sewed between the
layers, acts as a weight to hold the shelter over
the microphone. A hole in the center of the shel
ter allows a pin on the microphone to penetrate
Marker MC-693.
c. Cord CD-1238-A. Cord CD-1238-A con
sists of three lengths of single-conductor, shield
ed cable and one length of three-conductor,
shielded cable leading from a special connecting
5
VIBRATION
SHOCK
MOUNT
RELAY COVER
RELAY WRENCHES CAPACITOR C-52 FUSES
Figure 5. Recorder BC-1323-A, end view shoiving relay.
REAR COVER
TM2552A-5
box. The single-conductor, shielded cables are
15 feet long and are used to connect to the three
microphones forming the array. The three-con
ductor, shielded cable is 3 feet long and is used
to join Cord CD-1238-A to Cord CD-1239 which
connects to the recorder. Identification rings
are placed near each connector to insure connec
tion to its associated microphone.
d. Cord CD-1239. Each Bag BG-160-A con
tains three 50-foot Cords CD-1239. One end
terminates in a receptacle for connecting to
Cord CD-1238-A. The other end terminates in
a plug that connects to the recorder or to another
Cord CD-1239 as required.
e. Cord CD-1240. Cord CD-1240 is termi
nated at one end by a push-button switch and at
the other end by a connector plug. The plug end
connects to the recorder to permit the operator
to stop both recorders of a sound locating set at
the same time by remote control. If a longer
extension is desired, Cord CD-1239 may be in
serted between Cord CD-1240 and the recorder.
6
Figure 6. Bag BG-160-A and contents.
f. Chains. Three bead-type chains are sup
plied with Sound Locating Set GR-6-A. Two
Chains M-457 are each 15 feet long. The third
chain, Chain M-458, is 21 feet 21/2 inches long
(has the longest eyelets) . When the chains are
extended fully and properly set up, the fixed
microphone array assumes the shape of an isos
celes right triangle.
1 1 . Case CS—161 and Contents
Three Cases CS-161, two in use and one
7
spare, are included with each Sound Locating
Set GR-6-A. Each case (fig. 7) contains the fol
lowing components :
a. Handset TS-10-P. One sound-powered
Handset TS-10-P is packed in each Case CS-
161. It is used in conjunction with Reel Equip
ment CE-11 for telephone communication be
tween two recorder stations. For additional
information refer to TM 11-2250.
b. Headset HS-30-U. Each headset consists
of two Inserts M-300, two Receivers R-30-U,
Headband HB-30, Cord CD-620-U, Junction
Box JB-47, and 6VS> feet of extension Cord CD-
874. A saw-toothed clothing clip is attached to
the cord at the Y junction point. The extension
cord is terminated by phone Plug PL-55 for con
nection to the recorder.
c. Computor M-414 (fig. 8). Computer M-
N0.2 COUNTER READING AXIS
(HORIZONTAL AXIS)
NO.I COUNTER READING AXIS
(VERTICAL AXIS)
— BOTTOM DISK
/ (MIL SCALE)
«C V£ &
Figure 8. Computor M-AU.
TM2552A-8J
8
414 consists of two concentric plastic disks of
different diameters. A scale at the outer edge
of the bottom disk is divided into 64 main divi
sions, each of which represents 100 mils (total
is 6,400 mils) . The smaller divisions each repre
sent 10 mils. On the grid disk, which can be
rotated about the common center, each small
division represents two counter numbers. The
axis marked 1 is for the No. 1 counter reading,
and the axis marked 2 is for the No. 2 counter
reading. The arm on the computor may be ro-
-.VERNIER SCALE
tated through any point in the grid scale. This
arm has a calibrated scale from which the speed
numbers (par. S2d) are read for a given setting
of axes 1 and 2.
d. CorD CD-1446. Battery Cord CD-1446 is
6 feet long and has connector plugs on each end ;
one for the battery box and the other for the
recorder.
e. Marker MG-693. Marker MC-693 is a
small cube-shaped block with one side coated
with luminous material. When placed on the
O- INDEX LINE
:; jj MIL SCALE
' 7— V'7.;
2MQ0 30]OO l^lOQ 40|0O 45|OO 5O|pO
OO 3l50 4
Figure 9. Plotting Board M-10.
pin that is provided on the microphone shell,
the marker locates the microphone position at
night.
/. Plotting Board M-10 (fig. 9). Plotting
Board M-10 consists of an 8V2-inch rotatable
disk, of transparent plastic material, attached to
1t. Brush TL-72.
t2. Screw driver, 4-inch offset.
t3. Sandpaper (6 strips).
14. Pliers TL-304/U (long-nosed).
15. Pliers TL-t03 (side-cutting).
t6. Tweezers, 4 inch.
t7. Screw driver, 8 inch straight.
t8. Pliers (needle-nosed).
t9. Bag BG-44.
20. Flashlight TL-t22-D.
2t. Carbon tetrachloride (8-ounce
can).
22. Lubricating oil (4-ounce cans).
23. Cement.
24. Tubing, insulating.
25. Soldering iron.
BATTERY BOX CH-291
TM2552A-I2
Figure 12. Battery Box CH-291 complete with Batteries BB-51*.
a flat base. It is used to plot a base line and also
to determine target locations.
12. Bag BG-44
One canvas tool Bag BG-44 (fig. 10) is fur
nished with each set. Refer to figure 10 for a
list of the contents.
t. Tape TL-83 (friction).
2. Soldering paste.
3. TM 1t-2552A.
4. Tape TL-94 (splicing).
5. Solder M-3t.
6. Multimeter test leads.
7. Multimeter TS-297/U.
8. TM tt-5500.
9. Screw driver, 0-inch offset.
t0. Typewriter brush.
13. Multimeter TS-297/U
One Multimeter TS-297/U (fig. 10) is in
cluded for the maintenance and repair of each
sound locating set. It is used to check voltage,
current, and resistance. Refer to TM 11-5500
for complete details.
14. Reel Equipment CE—1 1
Two Reel Equipment CE-11 (fig. 11) are fur
nished. One reel is provided as a spare. This
11
equipment provides wire communication be- 16. Battery Box CH—318 and Battery BB—
tween the two recorders of the sound locating 221 /U
set. The equipment consists of a portable reel
with straps containing one-half mile of Wire Six Battery Boxes CH-318 (fig. 13) are
W-130 and Handset TS-10-P fitted with spring packed with each sound locating set. Battery
clips. For further details refer to TM 11-2250. Box CH-318 contains a 6-volt, lead-acid Battery
BATTERY BOX
CH-3I8
J-30I
TMZ552A-I3
Figure IS. Battery Box CH-318 complete with Battery BB-221/U.
15. Battery Box CH-291 and Battery BB-54
Twelve Battery Boxes CH-291 (fig. 12) are
furnished with each set. Each Battery Box CH-
291 is a container for three lead-acid Batteries
BB-54, connected with two jumpers and a har
ness to form a 6-volt power supply.
BB-221/U. This power supply is suited espe
cially for arctic operation.
1 7. Spare Parts
Running spare parts for Sound Locating Set
GR-6-A are as follows :
12
Quantity Description Quantity Description
1 Recorder BC-1323-A and Bag BG-182. 1 Holder M-167-A.
1 Bag BG-160-A. 1 Notebook.
2 Legs for recorder. 6 Pencils.
6 Microphone T-56. 1 Funnel.
6 Microphone Shelter M-413. 12 Tube, type 9001.
1 Cord CD-1238-A. 3 Tube, type 6AK6.
3 Cord CD-1239. 3 Tube, type 2AP1A.
1 Cord CD-1240. 3 Rectifier, selenium.
1 Cord CD-1444. 9 Lamp, incandescent.
1 Chain Kit MC-692. 15 Tape, recording.
1 Drill, star. 36 Fuse, 6-ampere.
1 Hammer TL-332/U. 33 Fuse, J^j-ampere.
1 Case CS-161. 12 Battery cap for BB-221/U.
1 Handset TS-10-P. 12 Battery cap for BB-54.
1 Headset HS-30-U and Cord CD-874. 1 Reel Equipment CE-11.
1 Computor M-414 in Case CS-148. 2 spools Wire W-130.
1 Cord CD-1446. 1 Flashlight TL-122-D.
3 Marker MC-693. 1 Lamp, neon, J^-watt.
1 Plotting Board M-10 in Case M-72.
1 Compass M-2.
CHAPTER 2
OPERATING INSTRUCTIONS
Section I. SERVICE UPON RECEIPT OF EQUIPMENT
18. General
a. Remove the nails with a nail puller ; prying
may damage the equipment.
b. Store the inside packaging materials in
their respective shipping containers for re-use.
Exception is made of the bags of desiccant or
dehydrating agent which will be either des
troyed or placed aside for reactivation.
c. Follow the steps outlined in paragraph 19
or all boxes 1/1 through 1/7.
1 9. Unpacking
a. Remove and save the packing slip.
b. Cut the metal straps.
c. Remove the nails with a nail puller and re
move the top of the shipping container.
d. Lift out the packaged unit.
e. Slit the waterproof barrier at the seams
and remove it from the package.
/. Slit the seal of the outer corrugated carton
and remove the moisture-vaporproof carton.
g. Slit the seal of the inner carton and open
the flaps.
h. Lift out all the corrugated fiberboard cells
and pads.
i. Lift out the contents.
j. Check all packaging for loose parts.
Section II. CONTROLS AND THEIR USE
20. Front Panel Controls
(fig. 14)
a. Volume Control (S5). The normal posi
tion of the VOLUME control knob is at the mid
point or on position 4. This knob controls both
the volume of the incoming signal and the vol
ume of the played-back signal. The pattern on
the scope should be adjusted to half-scale deflec
tion for the played-back signal. To increase de
flection, move the VOLUME control knob to po
sition 5, 6, or 7. To decrease deflection, move the
VOLUME control knob to position 3, 2 or 1. If
it is necessary to change the position of the knob
more than one point either way (increase or de
crease), it is advisable to make a new record
with the knob either on position 5, 6, or 7 or
position 3, 2, or 1 depending on whether the de
flection should be increased or decreased.
b. Scanning Wheel. The scanning wheel
moves the recording tape in either direction so
that the recorded signals on the tape can be lined
up manually with their respective heads.
c. Counter Adjustment Knobs. The count
ers No. 1 and 2 are adjusted by use of the count
er adjustment knobs. The counters measure the
time required for the sound wave to pass from
microphone M1 and microphone M2, respective
ly, to microphone M3, the reference point. If
microphones M1 and M2 are nearer the sound
source than microphone M3, the counters will
read between 000 and 150. The larger reading
is obtained when the respective microphone
(M1 or M2) is on the line connecting micro
phone M3 and the target. The smaller reading
means that the respective microphone is on a
line at right angles to the line connecting micro
phone M3 and the target. Intermediate readings
14
COUNTER ADJUSTMENT
KNOB NO. I
PUSH BUTTON
SWITCH (S3)
SCANNING WHEEL
COUNTER ADJUSTMENT
KNOB NO.2
PLAYBACK
LEVER (S2)
VOLUME CONTROL
IS5)
MAIN CONTROL
LEVER (SI)
TM 2552A-I6
Figure Recorder BC-1323-A, front panel controls.
will be obtained for intermediate positions. If
the sound wave reaches microphone M3 earlier
than either microphone M1 or M2, the counter
will read on the other side of zero, somewhere
between 000 and 850.
d. Main Control Lever (S1). The three po
sitions of the main control lever (S1) control
the operation of the recorder. In the up or REC
position, the main control lever permits simulta
neous recording of signals from the three micro
phones. In the neutral or STOP position, the
moving tape is stopped (but still can be moved
manually, with the scanning wheel (b above) ).
In the down or RUN position, the tape runs con
tinuously so that the recorded microphone sig
nals can be compared. (Signal comparison can
also be made in the STOP position.)
e. Play-back Lever (S2). With the main
control lever (S1) in the RUN or STOP posi
tion, the play-back lever (S2) permits a magnet
ic recorder or reproducer head to be substituted
for a microphone in each of the amplifier chan
nels, thus allowing the recorded signals to be
compared by manipulation of the scanning wheel
and counter adjustment knobs (b and c above).
The up or 1-2 position feeds the output of the
Nos. 1 and 2 recorder-reproducer heads into am
plifiers No. 2 and 1, respectively. (Monitoring
by use of Headset HS-30-U, while recording, is
carried on through amplifier No. 1.) In the neu
tral or 1-3 position of the play-back lever, the
output of the Nos. 1 and 3 recorder-reproducer
heads feeds into amplifiers No. 3 and 1, respec
tively. (Monitoring, while recording, is done
through amplifier 3.) In the down or 2-3 posi
tion, the output of the Nos. 2 and 3 recorder-re
producer heads is fed into amplifiers No. 3 and
2, respectively. (Monitoring, while recording,
is done through amplifier 2.) The position 1-2
may be used as a check on the 2-3 and 1-3 count
er settings. If the 2-3 and 1-3 adjustments are
correct, then the 1-2 setting will be in similar
adjustment.
/. Push-Button Switch (S3). Push-button
switch (S3) is a contact switch; when de
pressed, it causes the pilot lamps (E1 and E2)
to light up the counters.
15
21. Side Panel Controls
(fig. 15)
a. Power Switch Off-On (S7). This switch
is used to turn the recorder to the ON or OFF
position.
b. Focus Control (R68). The FOCUS con
trol is used to adjust the focus or sharpness of
the image on the oscilloscope.
c. Intensity Control (R66). The INTENS
ITY control is used to adjust the size and bright
ness of the image on the oscilloscope.
d. Radio — Survey — Off Switch (S4).
Switch S4 is used to connect microphone 3 input
to either the wire-line terminals or the radio
set. Its operation is complex and reference to
its use is explained in paragraphs 32, 33, 34, and
35.
Figure 10. Recorder BC-132S-A, rear cover removed.
16
e. Stop Button Switch (S101). When the
stop button switch on Cord CD-1240 of one re
corder is depressed, the magnetic relays (O-1)
of both recorders are energized. Their contacts
complete the magnetic clutch circuit and stop
movement of the tape of both recorders of Sound
Locating Set GR-6-A.
Section III. OPERATION UNDER USUAL CONDITIONS
22. Setting Up Equipment
For purposes of discussion in this technical
manual, the sound locating set to the right, when
line) is parallel to the enemy gun positions (fig.
17). If possible, the arrays should be sepa
rated by a distance equal to at least half the
estimated distance to the enemy guns. In any
ENEMY GUN POSITIONS
g g e
M3
BASE LINE
LEFT ARRAY RIGHT ARRAY
TM 2552A-I9
Figure 17. Base line between left and right arrays.
facing the enemy gun position, is designated as
the right array and is also the control operator's
station. The unit to the left is known as the left
array (fig. 17) . The sequence of steps in setting
up each azimuth measuring unit follows :
a. Selecting the site for the microphone array
(par. 23).
6. Setting up the microphone array (includ
ing determination of zero counter settings)
(par. 24).
c. Selecting the site for the recorder (par.
25).
d. Interconnecting the equipment (par. 26).
23. Selecting Site for Microphone Array
a. Set up the microphone arrays so that the
line connecting the two arrays (called the base
case, the arrays should be not more than 700
yards apart. Refer to paragraph 25 for infor
mation on selection of site for recorder and ra
dio.
6. Select a site for each microphone array
that is high, open, level ground (less than Vfc-
foot rise in 15 feet). Avoid proximity to roads
with heavy traffic, because traffic noise will in
terfere with the successful operation of the set.
Avoid deep valleys, densely wooded areas, spots
of thick grass or undergrowth, and areas of
grouped buildings. In general, the microphones
must be situated where the signals can be heard
above any interfering noise.
24. Setting Up Microphone Array
Zero counter settings on Recorder BC-1323
17
A must be determined before the microphones
can be set up as an array (fig. 18). The zero
counter settings obtain a correction factor that
is used in the computation procedures (par. 32) .
Proceed as follows :
a. Make the initial adjustment to the tape
mechanism as covered in paragraph 26.
6. Insert the connector of Cord CD-1238-A
(identified with one ring around the rubber in
sulation near the connector) into one of the
microphones which shall be designated as micro
phone M1. Repeat the procedure for the other
two microphones with the two-ringed cable con
nector inserted into microphone M2 and the
three-ringed cable connector inserted into the
microphone designated as M3. These micro
phone designations must be used later when the
microphone array is set up for normal opera
tion.
c. Attach the connector of Cord CD-1239 to
the free end of Cord CD-1238-A.
d. Insert the free end of Cord CD-1239 into
the receptacle on the recorder marked MICRO
PHONE.
e. Push the three microphones into the
ground at a distance between 10 and 12 feet
from the recorder. Each microphone must be
equidistant from the recorder and, therefore,
should be touching each other after insertion
into the ground. Clear the ground of all obstruc
tions immediately surrounding the microphones.
/. Insert the connector of Cord CD-1444 into
the recorder receptacle marked 6V and the
other end of the cable into the receptacle on
Battery Box CH-291.
g. Insert Headset HS-30-U plug into the re
corder jack marked PHONES.
h. Place the equipment into operation and
follow the operational procedures required to
obtain counter readings as explained in para
graph 32.
i. Fire a weapon at a point equidistant from
the three microphones or bring heavily gloved
hands together to simulate the effect of the muz
zle blast of a gun. Do not use the bare hands
for this purpose. If no gloves are available, use
layers of cloth wrapped around the hands. Re
peat this procedure two more times to make
three tests.
j. The average of the readings on each count
er is the true zero, and each average is taken as
follows :
(1) If the readings on a counter are all off
on the same side of zero, take the sum
of the readings and divide by the num
ber of readings. For example :
(a) If the readings on counter No. 1 are
003, 001, and 002, the sum of these
(006) divided by the number of tests
(3) would give the average true zero
for this counter as 002.
(6) If the readings on counter No. 1 are
997, 996, and 998, the average would
be 997.
Ml
Figure 18. Microphone array interconnections.
18
(2) If the readings on counter No. 1 are
on opposite sides of zero (for example,
997, 996, and 001), find the sum of the
variations from zero (000) on each
side of the zero, subtract the smaller
sum from the larger sum, and then di
vide by the number of tests. For ex
ample :
(a) The counter reading 997 is three
points from 000 and 996 is four
points from 000. The sum of the
variations on this side of zero is 7.
By subtracting 1, the variation on
the other side of zero, the result is
6. Divide 6 by the number of tests
(3) to get the average variation of
2.
(b) Because the larger sum was on the
900 side of zero, the average will be
reading is 906, subtracting two points
brings it down to 904.
(2) If the correction factor for counter
No. 1 is 998, add two points to counter
reading No. 1 for the total of 109 (107
plus 2) . The 906 reading becomes 908.
Note. A loosely assembled microphone can
cause the counter readings to go off by
more than four points. If both readings are
off from zero by the same amount, check
microphone M3. If the average zero is not
satisfactory for counter No. 1, check micro
phone M1. If the average zero is not satis
factory for counter No. 2, check microphone
M2. If both the counter readings are unsat
isfactory, by different amounts, check all
three microphones. Replace a suspected mi
crophone with the spare microphone and
repeat the tests. Repair the defective micro
phone if the test proves it to be necessary.
I. After the correction factor has been ob-
Figare 19. Microphone T-56, stake placed through eyelets.
on that side. The average true zero
for this counter, therefore, would be
two points away from zero on the
900 side, or 998.
(3) If the average of the readings on each
counter is four points or less away
from zero, the equipment is in satis
factory adjustment.
k. Apply the counter correction as follows:
(1) If the correction factor for counter
No. 1 is 002, subtract two points from
counter reading No. 1. For example,
the counter reading of 107, as obtained
in accordance with procedures outlined
in paragraph 32, becomes 105. If the
tained, proceed with the setting up of the micro
phone array as follows :
( 1 ) Shut off the recorder by throwing the
power switch to the OFF position.
(2) Pull all three microphones from the
ground, leaving the cables connected.
At position M1, place the stake of
microphone M1 (connected Cord CD-
1238-A has one metal ring) through
two eyelets of two separate chains
(one eyelet must be that of the long
chain) and push the stake into the
ground (fig. 19). The microphone
stajte should be pushed into the ground
by hand, as far as the stop on the
19
Figure 20. Microphone T-56, Cord CD-1238-A connected to microphone.
stake. At each microphone position,
press down or tear away the tall grass
underneath and around the micro
phone. If the ground is hard, use the
hammer and drill to make a hole for
the stake.
Caution: Do not drive the micro
phone into the ground with a hammer.
(3) Stretch the long chain to position M2.
Place the stake of microphone M2
(connected Cord CD-1238-A has two
metal rings) through two eyelets (one
eyelet being the other end of the long
chain), and set the microphone into
position as explained in (2) above.
(4) Stretch the remaining two chains to
position M3 and place the stake of
microphone M3 (connected Cord CD-
1238-A has three metal rings) through
two eyelets. Push the microphone into
the ground.
Note. All chains must be equally taut
Figure 21. Microphone T-56 and Marker MC-693 placed on top of microphone.
20
without disturbing the position of the micro
phone stakes.
(5) Add the required lengths of Cord CD-
1239 between the array and the record
er site.
m. Place Microphone Shelter M-413 and
Marker MC-693 over each of the microphones
as shown in figure 21. The shelter is not neces
sary if the weather is calm.
n. Set the compass not less than 5 feet di
rectly behind microphone M3 and in line with
the M1-M3 side of the array. Sight on the cen
ter of microphone M1 and read the magnetic
bearing of the M1-M3 side. Read and record
this bearing (it will be used as explained in
paragraph 32).
25. Selecting Site for Recorder and Radio
Choose a position for the recorder and radio
set that will afford adequate cover for the op
erator and good listening conditions. Avoid
locations near power lines, roads, electric mo
tors, or other sources of low-frequency noise-
interference.
26. Interconnecting Equipment
a. Initial Adjustments. After the recorder
is unpacked, make the following adjustment
under shelter.
( 1 ) Opening and removing covers.
(a) Turn the front cover latch counter
clockwise and pull the cover open.
(b) Turn the back cover latch counter
clockwise and pull off the cover.
(c) Loosen the five screws on each side
of the recorder until the side cover
clamping strips can be pulled away.
Place the recorder so that the carry
ing strap is on top of the equipment.
Pull off the cover.
(d) Remove the tape guard by loosening
the four knurled nuts shown in fig
ure 22.
Caution: Be careful when remov
ing the tape guard. Carelessness
will damage the steel tape, pole
pieces, and mechanism.
(2) Adjustment of tape-tension clamp
screw. Loosen, with the aid of a screw
21
driver, the tape-tension clamp screw
(0-4, fig. 46), so that the spring at
tached to the tension pulley (O-3) will
maintain constant tension of the pulley
against the tape. After this adjust
ment is made, replace the tape guard
and covers.
b. For Wire Line Operation (fig. 23).
(1) Connect Cord CD-1239 (from the mi
crophone array) to the recorder recep
tacle marked MICROPHONE.
(2) Remove Cord CD-1446 from Case CS-
161 and connect one end to the record
er receptacle marked 6V and the other
end to the receptacle J201 on Battery
Box CH-291.
(3) Connect Cord CD-1240 to the recorder
receptacle marked STOP SWITCH.
(4) Plug Headset HS-30-U into the jack
marked PHONES.
(5) Attach the running end of Reel Equip
ment CE-11 to the LINE posts on one
recorder and carry the reel to the other
recorder. Unreel sufficient wire so that
it may be passed through the LINE
posts of the second recorder. Do not
cut or skin the wire since the TM-175
LINE post pins pierce the insulation
and make contact.
(6) Attach the clips of Handset TS-10-P
to the HAND SET terminal posts.
c. For Radio Operation (fig. 24) .
(1) Perform the steps outlined in 6(1)
through (4) above.
(2) Connect one end of Cord CD-1444 to
the receptacle of Recorder BC-1323-A
marked RADIO.
(3) Connect the plugs at the other end of
Cord CD-1444 to respective jacks on
the radio set marked PHONE No. 1,
MIC, and RELAY.
(4) Connect radio Handset TS-15-A to
the recorder jacks marked RADIO
HANDSET.
Figure 24. Cording diagram for radio operation.
27. Equipment Performance Checklist
a. Purpose. The purpose of the equipment
performance checklist is to provide the operator
with a means of knowing whether the perform
ance of the equipment is normal or abnormal.
b. How and When to Use Checklist. The
items to be checked are grouped under three
headings : START, EQUIPMENT PERFORM
ANCE, and STOP. Check items 1, 2, and 3 to
start the equipment, items 4 through 6 for re
corder performance at each array position,
items 7 and 8 for wire-line operation, and items
9 and 10 for radio operation.
c. Checklist.
ItemItem
Actionor condition
Norma! indications Corrective measuresNo.
s 1 Power switch OFF-OX (87).
Push-button switch (S3)
Throw to ON position.....
Push
Dynamotor begins to run
with whirling sound.
Check 6-volt power
source. Check fuse F2.T
A 2 Pilot lamps illuminate
both counters.
Check pilot lamp or
lamps.R
T
*
3 Main control lever (Sl) Throw to STOP position... Small, needle sharp, fluor
escent spot on scope.
Adjust FOCUS control
(R68). Adjust IN
TENSITY control
(R66).
Place in RUN and REC
positions.
Scanning wheel rotates. Tape broken or off the
drive pulleys.
23
Checklist—Continued
ItemNo.
ItemAction
or conditionNormal indications Corrective measures
10
11
Stop button switch on Cord
CD-1240.
VOLUME control (85).
Main control lever (SI)
Playback lever (S2)._
VOLUME control (85).
Main control lever (SI)
Play-back lever (82)
Handset TS-10-P.
RADIO — SURVEY — OFF
switch (84).
Stop button switch on Cord
CD-1240.
Radio Set SCR-300-A
RADIO — SURVEY — OFF
switch.
Stop button switch on Cord
CD-1240.
Power switch OFF-ON
Push in..
Pull out..
Set to midpoint
Throw to REC position...
Throw to positions 1, 3,
and 2.
Set to midpoint
Throw to RUN position...
Throw to positions 1, 3,
and 2.
Talk into handset of wire
line equipment.
Throw to OFF position...
Tape stops if main con
trol lever (SI) is in
REC position.
Tape runs if main con
trol lever (SI) is in
REC position.
Audible signals from
microphone array on
Headset HS-30-U.
Audible pip signal on all
three positions of the
play-back lever.
Audible recorder signals
from the microphone
array.
Audible, intelligible
communication.
Push in at either array
Operate Radio Set
SCR-300-A with
out connecting to re
corder.
Throw to RADIO posi
tion.
Push in at either recorder.
Throw to OFF position...
Both recorders stop re-
cording (scanning
wheel stops rotating).
Communications estab
lished. Squelch circuit
operating.
Both recorders stop re
cording.
Dynamotor stops run
ning.
Check Cord CD-1240,
switch, and magnetic-
clutch solenoid coil
CL4) . Check relay
(O-1).
Check cables. Check
microphones.
Check pip circuit, elec
tron tube E6 or pip
head L9.
Check recorder or repro
ducer heads.
Check handsets. Check
wire line.
Check switch. Check coil
(L4) (clutch).
Refer to TM 11-242.
Check squelch circuit.
Refer to TM 11-242.
Section IV. OPERATION UNDER UNUSUAL CONDITIONS
28. Unusual Conditions
Sound Locating Set GR-6-A may be operated
under conditions of severe dust, moisture, and
temperature without damage to the equipment.
However, of operation under unusual conditions
is to be maintained for long periods, certain pre
cautions must be taken. Refer to paragraphs 29,
30, and 31 for information covering operation
under specific unusual conditions.
29. Operation in Arctic Climates
Condensation of atmospheric moisture occurs
inside the sound locating set components when
the units are exposed alternately to low and high
temperatures. Maintain as constant a tempera
ture as possible in the storage of the equipment.
Internal battery resistance increases with low
temperatures ; special battery care with particu
lar attention to higher charging rates is required
24
when Power Unit PE-210-( ) is used for
charging. Refer to TB SIG 66 for additional
winter operational information.
30. Operation in Desert Climates
Because of the numerous openings in the re
corder housing, precautions against the entry of
dust must be taken. A suitable equipment cover
may be improvised and placed completely
around the recorder after operation. Protect
Radio Set SCR-300-A, Power Unit PE-210,
Reel Equipment CE-11, and other associated
equipment as directed in their respective publi
cations. Consult TB SIG 75 for additional des
ert operational information.
31 . Operation in Tropical Climates
The recorder is a high-voltage device and, al
though adequately moisture-proofed and fungi-
proofed during manufacture, excessive moisture
between high voltage and ground may result in
the formation of leakage paths and voltage dis
charges. Damage to the varnish film must be
repaired immediately upon discovery. Cover
equipment whenever feasible to avoid drenching
during tropical downpours. Cover tightly after
use to conserve internal heat and reduce the pos
sibility of moisture condensation during the
cooler nights.
Section V. COMPUTING AZIMUTH AND RANGE
32. Finding Azimuth Angles
After the steps outlined in paragraphs 22
through 26 have been performed, the azimuth of
an approaching sound wave may be determined
by transferring the counter readings (obtained
from the recorder) to Computer M-414. The
procedure at each azimuth measuring unit (re
corder) follows:
a. Obtaining Counter Readings.
(1) Throw the power switch (S7) to ON.
Allow about 2 minutes for the recorder
to become warm enough to operate
efficiently.
(2) Throw the main control lever (S1) to
REC.
(3) Turn both counters to zero (000).
(4) Place the VOLUME control at posi
tion 4.
(5) Throw RADIO — SURVEY — OFF
switch (S4) to OFF for wire-line oper
ation or to RADIO for radio operation.
(6) Pull out the stop button at the end of
Cord CD-1240 to start the tape of both
recorders.
(7) When the muzzle blast of the target
weapon is heard, push in the stop but
ton switch on Cord CD-1240 ; this ac
tion stops the tapes on both recording
units.
Note. A ballistic sound wave is generated
by the passage of the missile through the air
and always will precede the arrival of the
muzzle wave. It will have a characteristic
crack compared to the thump of the muzzle
wave. To obtain the correct azimuth or count
er readings, the stop button must be pressed
on the muzzle wave.
(8) Throw main control lever S1 to RUN.
Make certain that the main control
lever S1 of the other unit is in the RUN
position.
(9) Start the tapes of both recorders by
pulling out the stop button switch on
Cord CD-1240.
(10) Put on Headset HS-30-U. Fasten
the clothing clip at a convenient place
on the uniform (lapel) .
(11) Throw play-back lever S2 to position
3.
( 12) The recordings from the three micro
phones will be heard in the following
sequence: pip, 3, 1, 2; pip, 3, 1, 2, etc.
(13) Throw main control lever S1 to the
STOP position during the microphone
M3 recording of the gun report.
( 14) Oscillate the scanning wheel with the
right thumb ; at the same time displace
it slowly downward until the initial
part of the 3 signal is located, as indi
cated by the sounds in the headset and
by the deflection pattern on the scope.
(15) With play-back lever S2 in the 1-3
position, the signals from the micro
25
phones at positions M1 and M3 may be
compared as follows :
(a) Observe the pattern on the oscillo
scope.
(6) Continue to move the scanning
wheel a short distance up and down
with the right hand. At the same
time, turn counter adjustment knob
No. 1 with the left hand until the
scope pattern approaches a vertical
straight line. To prevent injury to
the mechanism, avoid spinning the
counter adjustment knobs.
(16) Throw the play-back lever (S2) to
the 2-3 position to permit comparison
of the signals from microphones M2
and M3.
( 17) Observe the scope pattern while mov
ing the scanning wheel up and down
with the right hand. At the same time,
turn counter adjustment knob No. 2
with the left hand until the scope pat
tern approaches a vertical straight
line.
(18) Read and record the settings on
counters No. 1 and 2. Press the push
button switch (S3) to illuminate the
readings.
(19) Check the counter readings in the
1-2 position of the play-back lever
(par. 20e). The pattern observed on
the oscilloscope should be a vertical
straight line.
Note. Do not spend too much time in ob
taining satisfactory counter adjustments on
the 1-3 and 2-3 settings. If outside disturb
ances have been sufficiently great to make these
adjustments unusually difficult, it is advisable
to make a new record.
Computor M^14 Settings and Readings.
(1) Rotate the grid disk of Computor M-
414 until the arrow at the No. 1 coun
ter reading axis points to the magnetic
bearing of the M1-M3 side of the
array (par. 24i and fig. 25).
(2) Plot the point on the grid which is the
function of the Nos. 1 and 2 counter
readings which have been corrected in
accordance with procedure outlined in
paragraph 24.
(3) Move the computor arm until the red
line lies over the point.
MAGNETIC BEARING
(300 MILS)
GRID DISK
AZIMUTH ANGLE
(700 MILS)
COMPUTOR ARM
SPEED NUMBER
(39.7)
RED LINE
TM2552A-26
Figure 25. Computor M-4H, setting for azimuth angle of 700 mils.
26
(4) Read the value of the azimuth angle
on the bottom disk, under the red line
of the computor arm, to the nearest 10
mils.
(5) Read and record the speed number on
the red line of the computor arm at the
plotted point.
Note. The speed number is a constant based
on the velocity of sound and the traverse speed
of the tape. Consequently, the speed number
will hot change unless conditions prevail which
affect the velocity of sound or the traverse
speed of the tape. (Air temperature affects
the velocity of sound; battery voltage affects
the speed of the tape.)
(6) For example, suppose the M1-M3 side
of the array has a compass bearing of
300 mils, counter No. 1 reads 120 and
counter No. 2 reads 50. Figure 25
shows the setting of the computor.
The azimuth angle reads 700 mils. The
speed number reads 39.7.
(7) In another case, suppose the M1-M3
side of the array has a magnetic bear
ing of 200 mils, counter No. 1 reads
120 and counter No. 2 reads 950. Fig
ure 26 shows the setting of the compu
tor. The azimuth angle reads 6,200
mils. The speed number reads 39.7
c. Azimuth Angle Error. Because of at
mospheric conditions, the measured azimuth
angle may be 15 or 20 mils from the true angle.
Occasionally, an error of twice this amount may
occur. Therefore, if time and conditions permit,
obtain readings on more than one blast from a
target for higher accuracy. Since the tape re
cords for only 2 seconds, during which time the
air conditions change very little, it does not
help to measure more than one round on a
single record from the same target. However,
by the time the readings on one blast have been
made, air conditions may have changed enough
to warrant making another record. If a subse
quent comparison shows that these two angles
are close together (within 30 mils), compute
their average for the resultant azimuth angle.
If the angles are found to be widely different,
take another record ; select the two angles that
are closest together, and take their average. The
average is found by adding the two angles and
dividing by two. For example, if the two angles
were found to be 250 mils and 270 mils, their
average would be 260 mils. Compute as follows :
250 + 270
= 260
2
d. Use of Speed Number. The speed number
is used to compute the distance between an ar
ray and a point connected to it by means of a
wire line or a radio (pars. 33 and 34) . The speed
number should be checked from time to time.
If it is possible to find the counter reading
(straight-line adjustment) with one control, but
the scope pattern is so distorted that it is diffi
cult to find the counter reading with the other
control, the proper setting for the second control
can be approximated by means of the speed
number and the first counter reading. For ex
ample, suppose that previously measured sig
nals show a speed number of 40. A signal comes
in that gives a counter reading of 90 for the 1-3
position but the counter reading for the 2-3 po
sition is difficult to adjust. Then, if the compu
ter arm is moved until the speed number 40 rests
on the line through 90 on axis No. 1, it will indi
cate that the 2-3 counter reading should be
either about 92 or 908. The correct counter
reading will be determined by trial and, if pos
sible, by a consideration of the direction from
which the signal approached.
33. Finding Distance and Azimuth between
an Array and Another Point (Using Wire)
a. Finding Distance. This method can be
used only when the distance is not greater than
700 yards.
(1) Perform the steps described in para
graph 32a (1) through (4).
(2) Place the RADIO—SURVEY—OFF
switch (S4) to the SURVEY position.
(3) Fire a shot near the telephone at P
(fig. 27).
(4) When the report is heard by the re
corder operator (through the air at the
recorder position), stop the recording
by throwing the main control lever
(S1) to the STOP position.
(5) Put on Headset HS-30-U.
(6) Place the play-back lever (S2) in posi
tion 3, and place the main control
lever (S1) to the RUN position.
(7) The recordings of the three micro
phones and the wire line are heard in
the following sequence : pip, shot, 3, 1,
2 ; pip, shot, 3, 1, 2, etc.
(8) ' Place the main control lever on STOP
during playback of the muzzle blast
as recorded over the wire line. Do not
let the tape run between the measure
ments of the portions on the scanning
wheel of the wire-line report and mi
crophone report ((9) through (12)
below) .
(9) Oscillate the scanning wheel with the
right thumb ; at the same time displace
it slowly downward until the sounds in
the headset and the deflection pattern
on the scope indicate that the initial
part of the shot (recorded over the
wire line) is located.
(10) Read the scanning wheel by noting
the point on the scale of the wheel op
posite the white line on the panel. The
space between any two numbers is di
vided into 10 equal parts. Each of these
divisions is read as a tenth (.1). The
exact point should be estimated to the
nearest five-hundredth (.05). For ex
ample, if the scanning wheel were
stopped about halfway between 1.5 and
1.6, the reading would be 1.55.
(11) Move the scanning wheel upward
until the report (shot) recorded over
the microphone array is heard and no
ticed on the scope.
(12) As in (10) above, read the scanning
wheel for this report.
(13) Subtract the scanning-wheel reading
for the wire-line report ( (10) above)
from the scanning-wheel reading of
the microphone array report ((12)
above). The difference in readings
multiplied by the speed number equals
the distance in yards (c below).
b. Finding Azimuth Angle and Speed
Number.
(1) Throw the main control lever to the
RUN position. Throw the lever to the
STOP position on the 3 recording of
the gun report recorded over the array
(a (7) above).
(2) Oscillate the scanning wheel with the
right thumb and at the same time
displace it slowly downward until the
28
initial part of the 3 signal is located, as
indicated by the sounds in the headset
and by the deflection of the scope.
(3) Since the play-back lever (S2) is in
the 1-3 position, it permits the signals
from the microphones at positions M1
and M3 to be compared. This compar
ison is performed as follows:
(a) Observe the pattern on the scope
and continue to move the scanning
wheel a short distance up and down
with the right hand.
(6) At the same time, turn counter ad
justment knob No. 1 with the left
hand until the scope pattern ap
proaches a vertical straight line.
(4) Place the play-back lever (S2) in the
2-3 position to permit comparison of
the signals from microphones M2 and
M3.
(5) Observe the scope pattern and con
tinue to move the scanning wheel up
and down with the right hand. At the
same time, turn counter adjustment
knob No. 2 with the left hand until the
scope pattern approaches a vertical
straight line.
(6) Record the settings on counters No. 1
and 2. Check the counter readings as
explained in paragraph 20e. Do not
spend too much time attempting to ob
tain satisfactory counter adjustments
on the 1-3 and 2-3 settings. If outside
disturbances have been great enough
to make these adjustments very diffi
cult, make a new record.
(7) Plot the point on the grid correspond
ing to the Nos. 1 and 2 counter read
ings on Computor M-414 (par. 326).
(8) Record the azimuth angle and speed
number.
c. Computing Distance. To find the dis
tance in yards, multiply the speed number by the
difference in the scanning-wheel readings found
in a (13) above. Note example below.
(1) Suppose the scanning-wheel readings
are 1.55 for the wire-line signal and
9.00 for the microphone signal. Sub
tracting 1.55 from 9.00 gives 7.45 as
the number to be multiplied by the
speed number from the computor. If
the settings found in paragraph 32d
were 120 for the No. 1 counter reading
and 50 for the No. 2 counter reading,
the speed number found by the com
putor would be 39.7. Multiplying 39.7
by 7.45 gives 295.8 yards. Therefore,
the distance between the array (at mi
crophone M3) and the point (P) con
nected to it is 296 yards.
(2) If the scanning wheel, when turned
from the wire-line report to the micro
phone report, passes the 0 dial mark
ing, add 10 to the reading obtained for
the microphone report. (The scale has
only 10 divisions. When the wheel is
rotated through 10, it starts again at
1. To allow for each 10 divisions passed
through, 10 must be added to each suc
cessive reading.) Should a second
passing of the 0 reading be made, add
an additional 10 to this reading. For
example, if the scanning-wheel reading
for the wire-line signal is 9.5, and the
reading of the microphone signal is
3.5, and the wheel passes through 0
only once, then 10 should be added to
3.5, making it 13.5. Subtracting 9.5
from 13.5 leaves 4 as the difference of
the two readings. If the scanning
wheel passes through 0 twice when
going from the wire-line signal to the
microphone signal, 20 would be added
to the 3.5 before subtraction.
d. Recheck of Distance and Azimuth
Angle. To check the distance and azimuth
angle, repeat the steps outlined in a (3) through
c above.
(1) If the distances are within 5 percent
of each other, take their average as the
distance.
(2) If the angles are within 30 mils of each
other, take their average as the azi
muth.
(3) If the distances or angles are sepa
rated by too great an amount, repeat
the procedure until the two readings
fall within the above-stated limits
((1) and (2) above).
34. Finding Distance and Azimuth between
an Array and Another Point (Using Radio)
Make the following interconnections between
29
one radio set (Radio Set SCR-300-A) and the
recorder :
a. Connect one end of Cord CD-1444 to the
RADIO receptacle of the recorder.
b. Insert PHONE and MIC connector plugs
at the other end of Cord CD-1444 into PHONE
No. 1 and MIC jacks of the radio set. Do not
connect the relay connector plug of Cord CD-
1444 to the radio set, for it will stop the recorder
when transmitting.
c. Insert the radio Handset TS-15-A plug
into the recorder jacks marked RADIO HAND
SET.
d. The procedure for determining the dis
tance between an array and another point with
Radio Set SCR-300-A is similar to that used
with the wire-line method (par. 33a (1) through
(13) ) . The procedure for finding azimuth is ex
plained in detail in paragraph 32a. For instruc
tions on the operation of Radio Set SCR-300-A,
refer to TM 11-242.
35. Determining Base Line Distance and Azi
muth
a. Wire-Line Method. There are two meth
ods, when a wire line (Reel Equipment CE-11)
is used, for determining the base line distance
and azimuth. One method is explained in detail
in paragraph 33, in which point P (fig. 27) is
actually at the microphone M3 position of the
second (R) array. Performing the same steps
at the second (R) array and permitting the
point (P) to be located at the microphone M3
TELEPHONE
(HANDSET TS-IO-P)
TM 2552A-28
Figure 27. Surveying positions, using wire method.
position of the first (L) array will be a check on
the base line distance. (The azimuth, however,
will differ by 180° or 3,200 mils. The smaller
azimuth angle, in this case, will be at the left
(L) array as shown in figure 28.) In the other
method, the telephone is not brought out to the
array; instead microphone M3 is utilized in
place of the telephone. Interconnections are as
shown in figure 23. The shot is fired at each mi
crophone M3 position, and the base line distance
and azimuth are similarly determined as indi
cated above.
TM 2552A-29
Figure 28. Determining base line between two arrays.
b. Radio Method. The base line distance and
azimuth may be determined by means of Radio
Set SCR-300-A as outlined in paragraphs 32
and 34, respectively. However, it may be advan
tageous in some instance to determine the base
line distance without transporting the radio set
to the array positions. The procedure, in this
case, is as follows :
(1) Interconnect the equipment as shown
in figure 24, but omit connecting the
RELAY plugs of Cords CD-1444 to
the radio sets and handset plugs (PL-
068) to the recorders.
(2) Assume the sidearm will be fired at the
M3 position of the left array. Set the
left array recorder controls as follows :
(a) Power switch (S7) to the OFF po
sition.
(6) RADIO—SURVEY—OFF switch
(S4) to the OFF position.
(c) Stop button switch on Cord CD-1240
pushed in to start the transmitter.
(3) The right array recorder RADIO—
SURVEY—OFF switch (S4) is placed
to the SURVEY position.
(4) The procedure for determining the
base line distance at the right array is
30
similar to that for wire-line operation
(par. 33a (4) through (13)).
(5) Then check the base line distance at
the right array.
36. Surveying with Plotting Board M—10
After the azimuth of the target blast from
each array position (par. 32), the azimuth and
distance of the base line, and the azimuth and
distance of the counter battery (CB) have been
computed, plot these points (fig. 29) on Plotting
Board M-10 to locate the target (T) . Figure 29
is set up as an example, with given values, to
illustrate the procedure. Use figure 29 in con
junction with the subparagraphs below.
N
TM2552A-30
Figure 29. Locating the target.
a. Laying Off CB-R Azimuth. A vernier
scale has been provided at the edge of the base,
opposite the index arrow, in order to obtain
greater accuracy when laying off azimuths
which require interpolation between gradations
of the mil scale. The method below ( (1) through
(3) ) illustrates, for example, the steps to be
taken to plot the array positions and azimuth
angles so that the target range and azimuth
(from the counter battery position) can be read
off the plotting board.
(1) Set the gradation on the scale which
represents 380 mils opposite the 0
(red) line of the vernier scale (A, fig.
30).
(2) Count, on the vernier scale, six lines to
the right from the 0 line.
(3) Note the line on the mil scale which
lies next to, and outside, the 6-mil line
(the line further) on the vernier scale
and rotate the top dial until the two
lines coincide. The azimuth is now di
rectly opposite the index arrow as
shown in B, figure 30.
0 6
TM 2552A-3I
Figure 30. Using the vernier scale on Plotting Board
M-10.
b. Plotting Right Array Position. To plot
the right array, position R (after the dial has
been set to the azimuth of the CB-R line), sim
ply measure along the index line, using the nor
mal value of the grid squares for ranges less
than 2,000 yards, or using double the value of
31
Figure 31. Determining target range and azimuth on Plotting Board M-10.
the grid squares for ranges greater than 2,000
yards. Place a pencil mark directly on the index
line at the given distance (200 yards) .
c. Plotting Left Array Position. To plot
the left array, position L, rotate the dial so
that the index line is at the azimuth of the base
line R-L (5,200 mils). At point R, draw a
straight line parallel to the index line. Plot
point L at the given distance (500 yards).
d. Plotting Azimuth Angles from Arrays
to Target. Rotate the dial so that the index
line is set at the azimuth of the target from the
R array (6,000 mils). From point R, draw a
line parallel to the index line. Rotate the dial
so that the index line is set at the azimuth of
the target from the L array (90 mils). From
point L, draw a line parallel to the index line.
The intersection of these two lines fixes the
target position.
e. Reading Azimuth and Range of Target.
Set the target point over the index line (fig. 31 ) .
Read the target azimuth angle from the counter
battery position (6,114 mils). Read the target
range from the counter battery (1,175 yards).
37. Summary of Computation Procedure
(fig. 29)
The following is a summary of a complete
computation procedure :
a. Find the azimuth of the target from the
right and left arrays (par. 32) .
b. Find the azimuth of and the distance from
the counter battery position (CB) to the right
array (par. 33 or 34) .
c. Find the azimuth and distance of the base
line (par. 35).
d. Plot the counter battery (CB), the right
array (R), the left array (L), and the target
(T) positions on Plotting Board M-10 by fol
lowing the steps as outlined in detail in para
graph 36.
32
CHAPTER 3
MAINTENANCE INSTRUCTIONS
Section I. PREVENTIVE MAINTENANCE SERVICES
38. Definition of Preventive Maintenance
Preventive maintenance is scheduled work
performed on equipment during shut-down pe
riods to keep it in such good working order that
breakdowns and needless interruptions in serv
ice will be kept to a minimum. Preventive main
tenance differs from trouble shooting and repair
in that it eliminates certain troubles before they
occur.
39. Tools and Parts Supplied
Tools for maintenance are supplied with each
Sound Locating Set GR-6-A. The spare parts
are listed in paragraph 17.
40. Performing Preventive Maintenance
Perform the preventive maintenance opera
tions listed in a through c below at the intervals
indicated, unless otherwise ordered by the local
commander. Preventive maintenance for Radio
Set SCR-300-A, Power Unit PE-210, and Bat
teries BB-54 and BB-221/U must be performed
as described in TM 11-242, TM 11-947, TB SIG
90, and TM 9-2857, respectively.
a. Daily.
(1) Check the cords and cables for abra
sion and wear. Check connector plugs
and receptacles.
(2) Check the counter pilot lamps.
( 3 ) Check the battery level .
(4) Check for battery corrosion and loose
connections at terminals.
b. Monthly. Disconnect all power before
performing the operations below ( (1) through
(5)). Upon completion, reconnect the power
and check for satisfactory operation.
(1) Inspect the filter capacitors for leak
age of oil or dielectric, for bulging,
and for heating.
(2) Inspect the transformers for exces
sive heating.
(3) Inspect the fuses and fuseholders for
corrosion, cracks, and lack of tension
sufficient to insure good contact.
(4) Test the vacuum tubes; replace them
if necessary.
(5) Check and remove the accumulation
of sludge from the recorder and re
producer pole pieces with Solvent, dry-
cleaning (SD), and a clean, lint-free
cloth.
c. Quarterly. Make a visual inspection of
the following parts for the defects listed and
correct them if necessary :
(1) Tube sockets and pins for loose con
tacts, dirt, and corrosion.
(2) Filter capacitor terminals for corro
sion.
(3) Resistors for blistering, discoloration,
and other evidence of overheating.
(4) Switches for dirt, corrosion, loose con
tacts, and lack of snap action.
(5) Multiple connectors for dirt, corrosion,
and loose contacts.
(6) Wires, cords, and cables for cracked,
cut, or frayed insulation.
(7) Terminal boards for cracks, dirt, and
loose connections.
(8) Potentiometers for lack of smooth elec
trical and mechanical operation.
(9) Mountings, machine screws, and nuts
for mechanical looseness.
(10) All visible terminals and connections
for loose connections and corrosion.
(11) Varnish film (MFP) for breaks. (Re
touch with a brush if necessary.)
(12) Finish for scratches and bare spots.
(Retouch if necessary.)
(13) Insulators (terminal blocks) for
cracks and dirt.
33
(14) Selenium rectifier for loose connec
tions and dirt.
(15) Relay contacts for pits or build-ups
and for improper alinement. (Consult
TM 11-4302 for this information.)
Section II. LUBRICATION AND PRESERVATION
41 . Lubrication
a. General. Personnel responsible for lubri
cating Sound Locating Set GR-6-A must be
careful to apply lubricant only to the points in
dicated. Excess lubricant must always be re
moved.
b. Method of Applying Lubricant. Dip a
No. 22 gage wire about one-half inch into the
oil. Withdraw wire and apply the oiled tip to
the point specified. Use a clean, lint-free cloth
to remove excess lubricant.
c. Method of Cleaning Parts With Sol
vent (SD). Wipe parts with a dry, lint-free
cloth and then with solvent (SD). Pour a small
quantity of solvent (SD) onto a clean part of
the cloth or brush and apply the cloth or brush
to the part. Remove the cleaning residue with a
dry part of the cloth. Always clean before ap
plying the lubricant (if cleaning and lubricating
are specified).
d. Frequency of Lubrication. Apply lubri
cant and clean the recorder at least once every
month (weekly in tropical areas) .
e. Recommended Lubricant and Cleaner.
Sound Locating Set GR-6-A requires the use of
the following :
Approvedsymbol
Standard nomenclature Stock No.
PL-special.... Oil, lubricating, pre 14-O-2833-944 (Ord.)
servative special (4-
oz. can).
SD._ Solvent, dry-cleaning... 51-S-4385-1 (QMC).
/. Lubricating Details. Refer to figure 32
for location of the following parts which require
lubrication :
(1) Hinges. Apply 2 drops of oil (PL-
Special) along each hinge. Remove
excess oil with a clean cloth.
(2) Counter assemblies. Apply 1 drop of
oil (PL-Special) to the pinion shaft
at the point indicated.
(3) Magnetic tape and pole pieces. Re
move the tape (par. 60) . Wipe the ac
cumulation of dirt from the tape and
the recorder and reproducer pole pieces
with solvent (SD) and a clean, lint
free cloth. After the pole pieces are
thoroughly cleaned, apply oil (PL-
Special) to each of the pole pieces and
their pivots.
(4) Scanning wheel. Apply 2 or 3 drops of
oil (PL-Special) in the hole next to
the shaft.
(5) Tape pulleys. Put 2 or 3 drops of oil
(PL-Special) in each of the two holes
in the pulley above the dynamotor. Put
the same amount of oil in the hole
alongside the shaft of the pulley above
the counter assemblies.
(6) Tape wipers. Apply 1 drop of oil (PL-
Special) to each felt wiper pad.
42. Weatherproofing
a. General. Sound Locating Set GR-6-A,
when operated under severe climatic conditions,
such as prevail in tropical, arctic, and desert
regions, requires special treatment and main
tenance. Fungus growth, insects, dust, corro
sion, salt spray, excessive moisture, and extreme
temperatures are harmful to most of the mate
rials used in the construction of the equipment.
b. Tropical Maintenance. Although the
sound locating set is moistureproofed and fungi-
proofed, additional treatment may be required
in the field as a result of damage to the protec
tive varnish film. A special moistureproofing
and fungiproofing treatment has been devised,
which, if properly applied, provides a reasonable
degree of protection. This treatment is fully ex
plained in TB SIG 13 and TB SIG 72.
c. Winter Maintenance. Special mainte
nance information, useful under arctic condi
tions, is contained in TB SIG 66.
d. Desert Maintenance. Special precau
tions necessary to prevent equipment failures in
areas subject to high temperatures, low humid
ity, and excessive sand and dust are fully ex
plained in TB SIG 75.
e. Lubrication. The specified lubricant oil
(PL-Special) (par. 41) will provide adequate
lubrication under abnormal operating tempera
tures such as may prevail in the arctic and des
ert areas.
35
CHAPTER 4
FIELD MAINTENANCE INSTRUCTIONS
Section I. GENERAL
43. Field Maintenance Service
a. Purpose. The repair instructions in this
chapter are intended for use by field mainte
nance personnel trained and equipped to handle
complex repairs requiring special equipment
not generally available to organizational main
tenance personnel.
b. SCoPe. The scope of repairs that may be
performed by units having field maintenance re
sponsibility is limited only by the tools and test
equipment available and by the skill of assigned
personnel.
44. Recorder Mechanism
a. The recorder mechanism consists of a loop
of magnetic steel tape, two pulleys on which the
tape runs, three recorder-reproducer heads,
three erase heads, a pip signal head, three tape
wipers, a tape-tension adjusting mechanism, a
dynamotor, a magnetic clutch, and a scanning
wheel. When the covers and tape guard are re
moved, all except the scanning wheel may be
seen.
b. The magnetic steel tape is an endless loop
.002 inch thick, .050 inch wide, and 48 inches
long. It is on this tape that the signals, picked
up by the three microphones, are recorded. Fig
ure 46 illustrates the tape stretched between the
two pulleys which are mounted on a square tube.
Note also the magnetic heads and other com
ponents mounted on this square tube.
Section II. THEORY OF OPERATION
45. Overall Theory of Operation
a. Recording Process. The three signals
from the microphone array are fed through the
main control lever, S1, to the primaries of three
input transformers T1, T3, and T5. The out
puts of the transformers are then fed into three
separate amplifier channels as shown in the
block diagram (fig. 33). The output signal of
each amplifier is routed to its respective output
transformer and immediately recorded on the
magnetic tape loop by three separate recorder-
reproducer heads RH1, RH2, and RH3. Under
normal conditions of recording, the tape is auto
matically erased before recording, since the lo
cation of the erase heads immediately precedes
the recording heads in the direction of travel of
the tape. An additional amplifier V10 is used to
make the signals audible in the headset. A
fourth head placed in advance of the recorder-
reproducer head No. 3 is used to record a pip
signal so that identification of the recorded sig
nals can be made easily. An oscillator, V1 1, is
used to supply the necessary erase and bias cur
rents.
6. Play-Back Process. When the main con
trol lever, S1, is placed in the RUN position, the
signals that were recorder on the steel tape can
be played back and observed on the oscilloscope
screen as well as heard on the headset. Each
position of the play-back control lever, S2, per
mits the output from a pair of recorder-repro
ducer heads to be fed to opposite amplifiers.
(The exchange of the amplifiers tends to cancel
out any phase and amplitude errors inherent in
the amplifier channels.) The reproduced signals
after being amplified are fed to two deflection
plates of the oscilloscope. The open patterns
generally obtained on the scope indicate that
the signals, although identical in form, are not
36
<2
PIP| OSCILLATOR
EHI RHI
EH2 PIP
EH3 RH3
-I ->— MOVABLE
C-IO C-30
DYNAMOTOR
BLANKINGSWITCHIS-6]
OSCILLATORV-u6AK7
TO MICROPHONE ARRAY
i
MAIN CONTROL LEVER IS- I)
OUTPUT OUTPUT OUTPUTTRANSf TRANSF TRANSF
T-6 T-4 T -2
OUTPUTTRANSFT-7 HEADSET
ATH AUDIOAMPLIFIER
V-IO900I
CHANNEL NO. I
INPUTTRANSF
T- I
IST AUDIOAMPLIFIER
VOLUMECONTROLIS-5A)
2D AUDIOAMPLIFIER
3D AUDIOAMPLIFIER
V-3900I900I
V-2900I
T
INPUT
TRANSFT-3
I ST AUDIOAMPLIFIER
V-4900I
VOLUME
-H CONTROLIS-5B)
2D AUDIOAMPLIFIER
V-5900I
3D AUDIOAMPLIFIER
V-6900I
CHANNEL NO.2
INPUTTRANSFT-5
ISTAUDIOAMPLIFIER
V-7900I
VOLUMECONTROL(S-5C)
2D AUDIOAMPLIFIER
V-8900I
3D AUDIOAMPLIFIER
V-9900I
CHANNEL N0.3
PLAYBACK LEVERI S-2 )
TM 2652A-34
Figure S3. Recording operation, block diagram.
being reproduced simultaneously. However, ad
justment of the counters so that a straight-line
pattern appears on the scope indicates that two
signals are being reproduced simultaneously,
despite the fact that they were not recorded
simultaneously because of time differences in
the arrival of the sound wave at the two corre
sponding microphones of the array. The count
ers actually change the position of the movable
heads along the tape and represent the time dif
ference in arrival of the sound wave at the mi
crophones.
c. Computing Process. The azimuth angle
of the sound blast is determined by means of
Computor M-414. Setting up the azimuth of the
M1-M3 line as a reference and plotting the
counter readings enable the computor to de
termine the azimuth angle of the sound blast.
Duplicating the procedure at the other array
position determines another azimuth angle of
the same sound blast. The base line and counter
battery positions then are drawn on Plotting
Board M-10. The azimuth angles of the sound
blast from the counter battery position then is
easily read off the plotting board.
46. Amplifier Channels
a. The three amplifier channels Nos. 1, 2, and
3 are identical and are matched in gain, frequen
cy response, and phase shift. Consequently, one
simplified schematic drawing (fig. 34) is used
for functional explanation of its circuits.
6. Channel No. 1 consists of a three-stage,
resistance-coupled amplifier using type 9001
pentode tubes (V1, V2, and V3). The gain of
the amplifier is varied by an adjustable voltage
divider (VOLUME control (S5A)) in the con
trol grid of the second stage (pin No. 1 of tube
V2) . Seven fixed steps of attenuation, 6 db each,
provide a total gain variation of 36 db. Since
the maximum energy of muzzle blasts of small
arms fire lies in the frequency range from 60 to
300 cycles, the amplifier has been designed so
that its response is uniform within these limits
in order to reduce, to a minimum, extraneous
noises which would make adjustment of the
counters difficult. The low-pass filter (R-C (re
sistance-capacitor) networks, R1-C1 and R16-
C6) in the grid circuit of the first and third
stages and the plate-load capacitor, C7, in the
37
Figure 34. Recorder BC-1323-A, schematic diagram of one amplifier.
output of tube V3, are used to achieve the de
sired frequency response.
c. When the main control lever (S1) is in the
REC position, the signal from microphone M1
is fed to channel No. 1 through input transform
er T1. After passing through channel No. 1,
the signal is fed to another section of the main
control lever and then through V3 plate-load
resistor R20 and output transformer T2. The
plate-load resistor R20 forms the major part of
the load impedance for the output stage and is
selected high enough (220K) in relation to the
reflected impedance of the output transformer
primary (50K) to mask the variation due to the
recorder-reproducer head and to maintain the
constant output current required for a uniform
recorded frequency response. Signals from any
microphone can be selected by means of the
playback control lever and heard in the headset.
To monitor microphone No. 1, the playback con
trol is placed in position 1 ; microphone No. 3 is
monitored in position 3 ; and microphone No. 2
is monitored in position 2.
d. When the main control lever (S1) is in the
_i 11 ILLEH2 PIP
EHI RHI
T3
EH3 RH3
TS—FT
1 BLANKING|SWITCHIS-6I
INPUT
TRANSF.
T-5
INPUTTRANSF
T-l
IST AUDIOAMPLIFIER
V-l900,
VOLUMECONTROLIS-5A)
2D AUDIOAMPLIFIER
3D AUDIOAMPLIFIER
V-3900I
V-2900I
IST AUDIOAMPLIFIER
V-7900I
VOLUMECONTROL
(S-5C)
2D AUDIOAMPLIFIER
V-8900I
3D AUDIOAMPLIFIER
V-9900I
I 4TH AUDIO^ZZZ^ 1 AMPLIFIER
, V-IO900I
I MAIN CONTROL LEVER (S-l) I
T T T t -r
OUTPUTTRANSFT-T HEADSET
11111111PLAYBACK LEVER (S-2)
CHANNEL NO 3
TM 2552A-36
Figure S5. Recorder BC-1323-A, circuits used with playback lever in 1-8 position, block diagram.
38
(<5_
EH2 PIP
EHI RHI
JLJL
EH3 RH3 B---C
I BLANKING
| SWITCH(S-6)
OUTPUTTRANSFT-T HEADSET
4TH AUDIOAMPLIFIER
V-IO900I
Til 14-
I MAIN CONTROL LEVER (S- I) !
n—r t t t
INPUT IST AUDIOAMPLIFIER
VOLUMECONTROLIS-5B)
2D AUDIOAMPLIFIER
T-3V-4900I
v-s
CHANNEL N0.2
900I
INPUTTRANSFT-5
IST AUDIOAMPLIFIER
VOLUMECONTROL
2D AUDIOAMPLIFIER
V-7900I
(S-SCIV-8900I
3D AUDIOAMPLIFIER
V-6900I
3D AUDIOAMPLIFIER
V-9900I
CHANNEL N03 T
PLAYBACK LEVER IS-2)
9
TM 2352A-37
Figure 36. Recorder BC-1323-A, circuits used with playback lever in 2-3 position, block diagram.
(<5_
i I
Js Li.EH2
EHI
TT
pip
EH3 RH3
n—3T
BLANKING
SWITCH (S-6)j
-| DYNAMOTOR [
INPUTTRANSF
T-l
IST AUDIOAMPLIFIER VOLUME
CONTROLIS-5A)
V-l900I
CHANNEL NO. I
IMPUTTRANSFT-J
IST AUDIOAMPLIFIER
V-4900I
VOLUMECONTROL(S-3B)
2D AUDIO 3D AUDIOAMPLIFIER AMPLIFIER
V-2 V-3900I 900 I
2D AUDIO 3D AUDIOAMPLIFIER AMPLIFIER
V-5 V-6900I 900I
OUTPUT s—^TRANSF *-0 OT-7 UFAHCET
—r-
4TH AUDIOAMPLIFIER
V-IO900I
CHANNEL N0.2
1| 9001
1 Jtt
MAIN CONTROL LEVER IS-II
nlllll
PLAYBACK LEVER IS-2)
^scop^
TM 2552A-3B
Figure 37. Recorder BC-1323-A, circuits used with playback lever in 1-2 position, block diagram.
39
STOP or RUN position, the output from a pair
of recorder-reproducer heads is fed to opposite
amplifiers as shown in the block diagrams (figs.
35, 36, and 37) . In the 1-2 position of the play
back lever (S2), the recorded signals are being
reproduced in the headset amplifier through re
producer head RH1, in the 1-3 position through
reproducer head RH3, and in the 2-3 position
through reproducer head RH2.
47. Headset Amplifier and Blanking Switch
a. To monitor the microphones or heads, with
out disturbing the amplitude and phase response
of any channel, an isolation amplifier (fig. 38)
is used to feed Headset HS-30-U. By means of
the play-back switch the cathode of the third
stage of each amplifier is coupled through ca
pacitor C37 to the control grid (pin No. 1) of
tube V10. The plate load of the tube consists of
capacitor C40, inductance L3, and transformer
T7. Capacitor C40 and inductance L3 resonate
at approximately 500 cycles giving a uniform
overall response (from channel inputs to the
headset output) up to 700 cycles. This extended
range is necessary to increase the audibility of
the signals for monitoring.
b. Capacitor C36 and transformer T7 couple
the output of tube V10 to PHONES jack J5.
However, the secondary of the transformer is
grounded only through the blanking switch, S6.
REVERSE BLANKINGSWITCH, S-6
TO CONTROL 6RI0
PIN I0 OF V-I2
TAPE
This switch performs a dual function when mak
ing measurements on the recorded signals.
c. In the forward motion of the scanning
wheel (direction of tape travel during record
ing), the blanking switch grounds the second
ary, thus completing the headset amplifier cir
cuit. In the backward motion of the scanning
wheel, the blanking switch opens the amplifier
circuit and transfers the ground to the control
grid (pin No. 10) of the cathode-ray tube, V12,
thus effectively biasing it to cut-off. Hence, the
operator sees and hears the signal as it was
originally recorded.
48. Bias and Erase Oscillator
Tube V1 1, 6AK6, supplies both the bias and
the erase current for the recording system as
well as high voltage for the cathode-ray tube
accelerator anode (pin No. 7) . Audio frequency
oscillator V1 1 is connected as a triode (fig. 39) ;
the screen (pin No. 6) and the suppressor grid
(pin No. 2) are tied to the plate (pin No. 5) .
Its resonant frequency, approximately 8,000
cycles, is determined by the tank circuit consist
ing of tapped inductance L2 and capacitor C42.
The absolute frequency is not important and
may vary by 1,000 cycles without affecting per
formance of the equipment, provided the fre
quency is reasonably constant and the output
voltage is stable. Positive feedback is applied
to V11 control grid through coupling capacitor
C41. Voltage drop across the grid-leak resistor,
R72, develops grid bias for the tube. The bias
and erase voltage for the recording system is
taken from the plate circuit through coupling
capacitor C31. A portion of the oscillator out
put is also fed to the recorder-reproducer heads
(through capacitors C10, C20, and C30) , so that
:c-36
TO AMPL „OUTPUT ■+ f-VIA S-2 n
r±r TM2552A-39
Figure 38. Headset amplifier and blanking switch,
simplified schematic diagram.
TM 2552A-40
Figure 39. Bias and erase oscillator, simplified
schematic diagram.
40
both the audio signal and the 8,000-cycle biasing
voltage are present simultaneously during re
cording. This high-frequency biasing voltage
on the heads results in a better signal-to-noise
ratio and less distortion.
49. Pip Signal
a. Identification of the signals would be prac
tically impossible were it not for the tone or pip
signal recorded on the steel tape during the
recording process. This identifying signal is
generated by a 250 cps (cycles per second) re
laxation oscillator consisting of resistor R78,
capacitor C51, and glow tube E6, as shown in
the simplified schematic (fig. 40) . The pip head
(mounted on the same base with the No. 2 erase
head) is placed between the recorder-reproducer
heads Nos. 2 and 3 and records the continuous
identifying tone whenever the main control lev
er (S1) is in the REC position. On playback,
the recorded signals appear in the scope and
headset in the following sequence : pip, 3, 1, 2 ;
pip, 3, 1, 2; etc. Since the pip head is mounted
slightly in advance of the No. 2 erase head, the
erase head clears everything off the tape except
the small portion between the heads.
C-5t R-78
i 1( f <VW * B+ THROUGH,v MAIN CONTROL
LEVER S-l
I PIP
1 \JMLr • □_
L-9 ~
TM 2552A- 41
Figure U0. Pip circuit, simplified schematic diagram.
b. When the main control lever, S1, is in the
REC position, the glow tube, E6, shunted across
series-connected capacitor C51 and pip head in
ductance L9, is connected to the B-f supply
through resistor, R78. Hence, the B-f supply
charges the capacitor. When its voltage becomes
equal to the starting (ignition) voltage of the
tube, the glow discharge takes place and the
capacitor discharges through the tube down to
a voltage equal to the extinction potential at
which the tube goes out and the capacitor begins
recharging again. This charge and discharge
cycle (250 cps) is repeated continuously as long
as the supply voltage is maintained. The cur
rent flowing through the pip head records this
250-cps rate as an audible tone.
50. Power Supply and Voltage Doubler
a. All plate and screen voltages for the re
corder unit are obtained from the 230-volt, d-c
output of the dynamotor, D1. The heater volt
ages are provided by the 6-volt battery supply.
The higher accelerating voltage necessary for
the cathode-ray tube is obtained by the addition
of a half-wave voltage doubler circuit to the two
filter sections of the power supply as shown in
figure 41.
6. Operation of the voltage doubler is as fol
lows : assume for the initial half cycle that point
A on the oscillator tank circuit is positive with
respect to point B. Current then flows through
the selenium rectifier, CR1, and charges capaci
tor C43 to the oscillator peak voltage. During
the next half-cycle as point B becomes positive
with respect to point A, the charge of capacitor
C43 will add its potential to that of point B and
current will flow through the selenium rectifier,
CR2, thus charging capacitor C47 to twice the
oscillator voltage. Since the common input and
output terminal, point D, of the voltage doubler
circuit is in series with the dynamotor output
supply, the total voltage at point C is equal to
the sum of the voltages of the dynamotor output
and the voltage doubler.
51. Cathode-ray Tube
(fig. 42)
a. The control grid bias and focusing voltage
for the cathode-ray tube, V12, type 2AP1-A, is
obtained from the voltage divider consisting of
two potentiometers, R68 (FOCUS control) and
R66 (INTENSITY control), and resistor R67.
For operation, the focusing anode (pin No. 4)
is approximately 100 volts positive (terminals
28 to 27) with respect to the cathode (pin No.
2) ; its value is adjusted by means of the FOCUS
control, R68. The control grid (pin No. 10) is
approximately 10 volts negative (terminals 26
to 27) with respect to the cathode; its value is
adjusted by means of the INTENSITY control,
41
TO PIN 5 OF
OSC V-ll
217V PEAK
TO DYNAMOTOR
D-l
*
VOLTAGE
DOUBLER
♦> 670V
TO SCOPE
R-76
MAM
C-48-C
B -h
215 V
Figure Power supply and voltage doubler, schematic diagram.
TM 2552A-42
R66. When the main control lever (S1) is set
on REC, the control grid becomes grounded. The
increased grid-to-cathode potential effective
ly biases the control grid to beam cut-off. A re
sistor, R65, is used as a current limiting resistor.
b. The output from a pair of amplifiers (se
lected by the main control lever (S1) and play
back lever (S2)) is connected to the deflection
plates (pins No. 3 and 9) of the cathode-ray
tube through coupling capacitors C32 and C33.
Each deflection plate has a low-pass, R-C net
work (R61-C35, R63-C34) to provide additional
high-frequency attenuation to that obtained in
the amplifier circuits. The deflection plates are
at the same d-c potential as the accelerator anode
(pin No. 7) through resistors R62 and R64.
Section III. PREREPAIR PROCEDURES
52. Test Equipment Required tial Mogt troubles can be traced with the Multi.
To service Sound Locating Set GR-6-A prop- meter TS-297/U which is furnished as a com-
erly, the test equipments listed below are essen- ponent.
42
C-32
CATHODE RAY
V-12
2API-A
C-35
TO AMPL
OUTPUT VIA
S-l a S-2
R-66
INTENSITY
HI V
670 V
240 V
TM 2552A-43
Figure 42. Cathode-ray tube circuit, schematic diagram.
Signal Corpsstock No.
Item Used for Remarks
3F4325 297 Multimeter TS-297/U Checking against voltage Furnished with equipment.
3F3559.. Oscillator 1—151 or equal
resistance charts.
Audio tests
3F3630-1060..._ Oscilloscope BC-1060 or equal
Electronic Multimeter TS-505/U....
Checking tape speed and
3F4325-505._
signal tracing.
Making gain measurements.. Vacuum-tube voltmeter
should have at least 10-
megohm input impedance.
53. Power Requirements
A power source of 110-volt, 60-cycle ac (alter
nating current) is required for the test equip
ment listed in paragraph 52. A 6-volt battery
supply is required for the sound locating set.
54. Opening and Removing Covers of Re
corder BC-1323-A
a. To open the front cover, turn the front
cover latch counterclockwise and pull the cover
open.
43
b. To remove the back cover, turn the back
cover latch counterclockwise and pull the cover
off.
c. To remove the left side cover, loosen the
five screws on each side of the recorder until
the side cover clamping strips can be pulled
away. Place the recorder so that the carrying
strap (left side cover) is up. Pull the cover off.
d. To remove the right cover, place the re
corder so that this side is up. Pull the cover off.
e. To expose the tape, heads, etc., remove the
tape guard by loosening the four knurled nuts
shown in figure 22.
Caution: Be careful when removing the tape
guard. Carelessness will damage the steel tape,
pole pieces, and mechanism.
Section IV. TROUBLE LOCATION
55. General
Faults should be located by following an or
derly and systematic procedure with the pur
pose of first determining whether the trouble is
in an input circuit, an output circuit, the power
supply circuit, an oscillator circuit, or an ampli
fier circuit. After the defect is traced to one of
these sections, the fault should be isolated fur
ther to components, and tubes should be checked.
The signal should be traced from stage to stage
to determine where the failure occurred. A trou
ble-shooting chart (fig. 45) is provided to assist
in locating faults. Illustrations showing parts
location will assist in identifying the various
components when voltage and resistance meas
urements are made. Consult schematic dia
grams (figs. 38 and through 42). Block dia
grams (figs. 35 through 37) and over-all sche
matic diagrams (figs. 54 through 62) are also
provided.
56. Specific Faults and Remedies
a. Magnetic Tape Control. A relay, O-1,
is used to operate the clutch solenoid, L4, in re
sponse to 6 volts applied to a telephone (wire)
line by means of the stop button switch at a re
mote point. However, if the relay coil becomes
open-circuited or if the contacts fail, remote
control of the tape drive becomes impossible.
In such a case, the recorder (with the defective
coil) should be wired to include a jumper from
terminal board, E12 (lug 2), to stop switch, J4
(pin D), and should be used in the control posi
tion so that the control operator will be able to
2.I v
122 K 6.8 K I22K 6.8 K
5.8V 5.8V
IMEG 6.8 K
GND.
500 K 500 K
<§iK2.ov rf 3.8 V
6.8 K 0
50 V 115 V
2 MEG 500 K
TM 2552A-49
Figure 43. Tube socket voltage and resistance vieasureinents.
44
stop the recorder at the remote position with the
good relay.
Caution: This jumper should be used only in
an emergency. The defective coil should be re
placed as soon as possible.
b. Microphones and Amplifiers. Set the
main control lever, S1, in the REC position.
Note whether a large difference in volume level
is noted in the headset as the play-back lever is
switched to channels Nos. 1, 2, and 3. An inter
change of microphones will show whether dif
ferences of response exist between microphones
or between amplifier channels. For example, if
comparatively low volume response is noted in
channel No. 3 and again in channel No. 1 after
interchanging microphones M3 and M1, the mi
crophone originally at M3 is defective and
should be replaced. On the other hand, if the
response in channel No. 3 remains low after
interchanging the microphones, channel No. 3
is defective (figs. 43 and 44). Replace the type
9001 tubes. Microphones may be opened and
checked (fig. 51).
57. Audio Stage Gain Chart
Note. The audio gain measurements listed are made
under the following; conditions: All voltages are mea
sured to ground with a vacuum-tube voltmeter having
at least a 10-megohn input impedance. Oscillator tube
V11 is removed from the socket. Maximum signal fed
to the microphone connector, J-1 (pins B, C, and D),
is .006 volt at 100 cps. The main control lever, SI, is
in the REC position. Signal to heads (at terminals 5,
6, and 8 of E11) = .065 volt.
Stage
T1, T3, T5.
V1, V4, V7 _
V2, V5, V8.
V3, V6, V9._.._
V3, V6, V9.___
V10
T7*
Input
Pin orterminal
i
i
i
2 and 7
1
5
Volts
0.006
.145
.060
1.380
1.000
.980
1.300
Output
Pin orterminal
Volts
0.18
3.90
1.56
25.00
18.00
.07
Voltagegain
30
27
26
18
18.2
* Headset HS-30-U is connected to PHONES receptacle J5.
58. Voltage and Resistance Measurements
The voltage and resistance measurements of
Recorder BC-1323-A are shown in figures 43
and 44. Measurements at the cathode-ray tube
socket and the terminal boards are listed in
tabular form below. Measurement conditions
are as follows :
a. Voltage and resistance measurements are
taken to ground with a 20,000-ohm-per-volt
meter.
6. Battery voltage is 5.8 volts at battery con
nector P2.
c. Measurements are taken with all tubes
(except V12) in sockets, VOLUME control set
on 4, R66 (INTENSITY) on full, R68 (FO
CUS) on full, play-back lever on 1-3 position,
and main control lever on REC, unless otherwise
noted.
d. Resistance measurements (fig. 43) are
taken with power source removed.
e. All voltages in the following table are dc
unless otherwise noted :
Ref.symbol
TerminalSI on RKC
(volts)SI on STOP
(volts)Resistanee(ohms)
E1l i 0
2 5.8 20
3 5.8 20
4 5.8 5.8 3
5 9.2ac 30
6 15. ac 30
7 0
8 9.0ac 30
9 85 . 0 ac CO
E9 10 215.0 220.0 2.6 K
11 0
12 225 0 230.0 50 K
13 21.0 120 K
14 CO
15 oo
16 0
17 85.0 ac 150.0 ac CO
18 28
19 5.8 5.8 3
20 0
K7 21 N.C.*
22 OO
23 5.8 5.8 9
24 1.2 K
25 0
26 40.0 50.0 0
27 50.0 60.0 24 K
28 180.0 187.0 32 K
29 240.0 245.0 200
30 240 0 245 0 200
31 5.8 5.8 1
32 2
E8 33 445 . 0 620.0 CO
34 445.0 620.0 oo
35 CD
36 00
45
Ref.Symbol
TerminalSI on REC
fvolts)SI on STOP
(volts)Resistance
(ohms)
X12 1 5.8 5.8 3
2 50.0 60.0 24 K
3 430.0 600.0 CO
4 180.0 187.0 30 .6 K
5
6 480.0 670.0 CO
7 480.0 670.0 CO
8 480.0 670.0 CO
9 430.0 600.0 CO
10 45.0 100 K
11 0
* X. C.—Xo connection.
59. Trouble-shooting Chart
The trouble-shooting chart shown in figure
45 lists the corrective measures to be taken by
the trouble-shooter for the symptoms given. The
chart is sectionalized into four units : 6-volt
battery, dynamotor, record, and playback. Use
the chart as follows :
a. Starting with the battery, note that the
words LOW VOLTAGE appear to the left of
the rectangle labelled 6-VOLT BATTERY. In
this case, LOW VOLTAGE is the symptom; fol
low the arrowheads to the left of the symptom ;
the arrow heads terminate at another rectangle
which contains the checks to be made in order
to find the causes of the low voltage. The cor
rective measures in this case are indicated by
the checks.
b. Following the arrowhead down the chart,
note two more rectangles containing the words
DYNAMOTOR and TUBE FILAMENTS. By
continuing in the direction of the arrowheads,
the symptoms and checks will be located on the
chart.
c. The same method is used for the balance of
the chart; namely, RECORD and PLAYBACK.
46
-CHECKVOLTAGE
6- VOLTBATTERY
FUSE.F-2swrrcH.a-7BRUSHES
OIRTT COMMUTATOR
DEFECTIVE- DOES NOT RUN
HEADSET.TUBE V-IOING SV». S-6
AMPL.BLANK
DEFECTIVENO SIGNAL
-AUDIBLE INHEADSET INANT POSITION
4
TUBEFILAMENTS
. DO NOTLIGHT "
DEFECTIVE FUSE.HSWITCH.S-7
RUNS OK.
WITH S-l IN REC. POS B VOLUME CONTROL IN PCINTRODUCE A I00 CPS SIGNAL OF .002 VOLTS 1MICROPHONE CONNECTOR, J-l (PINS B,C,D)
1.I,
CHANNEL IVI,V2,V3
RECORD|-*S2INI-2POS. P NO
» - S-2 IN 2-3 POS. AUOIBLE ?!S-2 IN I -3 POS. |_SIGNAL_J-i—[*'
DEFECTIVEAMPLIFIER
CHANNEL 2
V2,V3,V«
CHANNEL 3V5,V6,V7
| PLATBAClT
CLUTCH SOLENOIDL-4
,OEFECTIVE TAPE DOES- NOT STOPRUNNING
|R-«LR-62,R-6J,R-64p-32jC-33.C-34.G-35
DEFECTIVE
CRT V-I2R-23.R-65
H i v. Supply(CR-I.CR-2)
NO SPOTON CRTSCREEN
IMPOSSIBLE„„„,„. TO ADJUST.DEFECTIVE CRT FOR
■ SUFFICIENT
BRIGHTNESS
L-9.E-6.C-5IR-78,S-l,S-2
DEFECTIVE _PIP SIGNAL
INAUDIBLE
EXCESSIVE PHASESHIFT IN AMPL. IOR 3. CHECK ALLCOMPONENTS
COUNTER NO. I MUSTBE MOVED MORE THANTV/0 DIVISIONS FOR "STRAIGHT LINE.
ADVANCE SIGNAL360(APPR0X.»OCOUNTER DIVISIONS)
WITH S-l IN STOP POS.
TAPE» STOPSRUNNING
EXCESSIVE• NOISE *\
SPUTTERINGMICROPHONICS "
DEFECTIVEAMPL TUBE
DYNAMOTOR NOISE -
WITH S-l IN RUN POS.
..EXCESSIVE NOISE
ON TAPE
LISTEN WITH PHONES
DO NOT HEARTHREE SIGNALS
-BETWEEN PIPS -IN ALL THREEPOS. OF S-2
GROUND LOOP DUE T0[HEAD ct'T GROUNDED!
AT CARRIAGE
r
POOR ERASE - -{erase HEAD OSC V-ii]
POOR TAPE CONTACTDUE TO
DIRTY POLE PIECES
, NO SIGNAL J
HEARD
- POS.Kl-2) - HEAD RHI
POS. 3 (I-3) - HEAD RH3
-POS. 2 (2-3)- HEAO RH 2
SWITCH CONTACTSS-l,S-2 OR
TRANS.T-2,T-4,T-6
ALL SIGNALS NO LISSAJOUS DEFECTIVE S-2,C-32,C-33,AUDIBLE " FIGURES R-6I.R-64
WITH S-2 IN I-3 POS.
WITH S-2 IN 2-3 POS.
COUNTER NOl MUST BEtoMOVED MORE THANTWO DIVISIONS FORSTRAIGHT LINE
EXCESSIVE PHASE
SHIFT IN AMPL. 2CHECK ALLCOMPONENTS
-STRAIGHT LINE PATTERN WAVERS -DEFECTIVE
*j PLANETARY DRIVE
TM2552A-I4
Figure U5. Trouble-shooting chart.
47
Section V. REPAIRS
60. Removing and Replacing Magnetic Tape
(fig. 46).
a. General. The magnetic tape must be re
moved whenever the recorder is being cleaned
and oiled. If a tape is broken accidentally, install
a new one. Be careful when handling the tape
because it may be kinked or broken easily.
b. Removing Tape.
(1) Hold tension pulley, O-3, at one end
of the tension arm and loosen the tape-
tension clamp screw, O-4, at the other
end of the arm.
(2) Swing the tension arm away from the
tape wipers to separate the pads and
lift the tape from between them.
(5) Loosen the holding screws (fig. 47)
and pull out the top sapphire guides
just enough to clear the tape.
(6) Lift the tape from between the pole
pieces by opening the jaw of each pole
piece, one at a time, and by slipping
the tape out.
Caution: Do not permit the pole
pieces to spring back against the tape
as a kink in the tape might result.
(7) Slide the tape off the pulleys and lift
it out.
tape and tighten the clamp screw so
that the arm can be held in that posi
tion.
Caution: Do not release the tension
pulley until the clamp screw has been
tightened. Should the pulley be re
leased while the clamp screw is loose,
the spring may snap the pulley against
the tape and break it.
(3) Remove the shield inclosing signal
heads RH3 and EH3.
(4) Pull down the arms on the side of the
c. Replacing Tape.
(1) To replace the tape, follow the steps
outlined in 6(1), (2), (3), (4), and
(5) above.
(2) Pull down the arms on the side of the
tape wipers to separate the pads.
(3) Place the tape over the pulleys. Note
the weld in the tape. It should face the
outside as shown in figure 47. If the
movable pole piece is not closer to the
weld than the fixed pole piece in the
direction of tape travel, serious dam
48
TOP
SAPPHIRE GUIDE-
HOLDING
SCREW
BOTTOM
SAPPHIRE GUIDE
TM 2552A-5I
Figure 47. Recorder-reproducer head, details.
age to the tape and pole pieces may
result.
(4) Insert the tape between the pole pieces
by opening the jaw of each pole piece
one at a time. Ease the pole piece back
against the tape very carefully.
(5) Push the top sapphire guide into place.
Adjust sapphire positions by rotating
the sapphire guides so that the tape
rides evenly between the top and bot
tom sapphires. Tighten the holding
screws.
Caution: Sapphire guides must hold
tape firmly in position without causing
the tape to twist. A loose tape will
cause phase errors during playback.
(6) Adjust the tape wipers and replace
the magnetic head shield.
(7) Repeat the step described in (1) above.
(8) Let the tension pulley come up slowly
against the tape as far as it will go and
then release it. Do not release the ten
sion pulley until it is firmly against
the tape.
(9) Rotate the scanning wheel a short dis
tance downward so that the tape re
volves in a clockwise direction. This
will even up the tension on the tape.
( 10 ) Tighten the tape-tension clamp screw.
61 . Replacing Dynamotor or Brushes
(fig. 48)
There are four dynamotor brushes, two on
each end of the armature. Replace the brushes
or the dynamotor as follows :
a. Remove the shield (by removing three
£-t2 F-3 F-l F-2 R-67
R-75 R-76 £-8 E-9 E-IO V-IO R-22 R-2I R-2 c.„ c-, £.H
„ . ._. . _ _. .. -' Kji Til
Figure 48. Recorder BC-1S2S-A, right side cover removed and side panel parts exposed.
49
screws holding it to the chassis and two screws
on rear panel).
b. Unsolder the three wires on the magnetic
clutch coil, L4.
c. Remove the two screws holding the dyna-
motor to the shock mounts.
d. With the side panel up, remove the four
screws holding the dynamotor mounting plate
to the planetary drive.
e. Carefully lift the dynamotor out so that
the wires do not tear away from the soldered
joints. To replace the dynamotor, carefully re
move the attached components and reinstall
them on the new dynamotor.
/. To remove a brush, take out the screw (at
the bottom of the brush holder) that fastens
the brush holder to the dynamotor.
g. Unsolder the brush lead wire from the lug
on the outside of the brush holder.
h. Note the position and type of brush and
remove it from the brush holder.
i. Put a new brush of the same type in the
same position as the old brush. Solder the lead
wire to the lug.
j. Replace the brush holder and tighten in
place by means of the screw which was removed
in the step described in / above.
50
CHAPTER 5
SHIPMENT AND LIMITED STORAGE AND
DEMOLITION TO PREVENT ENEMY USE
Section I. SHIPMENT AND LIMITED STORAGE
62. Packing Equipment for Shipment
a. See that all components and accessories are
at hand by consulting the packing slip or the
list of parts in paragraph 5.
b. Prepare seven wooden boxes to house all
the equipment of a complete Sound Locating
Set GR-6-A. Size of boxes shall be the same
as those used to ship the equipment (export
packed). If original boxes are available, use
them.
c. Place corrugated fiberboard cells and pads
on the bottom and sides of all boxes.
d. Place the three recorders in their respec
tive cartons and heat-seal them into moisture-
vaporproof bags. Place the cartons with their
moisture-vaporproof bags into a waterproof
container and place the three similarly wrapped
recorders in their respective boxes.
e. Heat-seal the waterproof bag and cover
the top with corrugated pads and cells. Do this
for the three recorders.
/. Nail wooden box covers in place and mark
the box to identify contents.
g. Place Bag BG-160-A and contents into the
fourth box after making sure the proper cush
ioning and waterproofing steps have been taken.
Cover box and identify contents with appropri
ate marking.
h. Place Case CS-161 and contents into an
other box after proper packing procedure.
i. Place the balance of the equipment into the
sixth box (except batteries).
j. Carefully cushion the batteries and place
them into the seventh box. Make sure electro
lyte will not spill. Mark the box appropriately
to warn handlers that it contains acid which
may spill.
63. Repacking for Limited Storage
a. Clean and dry the equipment.
b. Place the equipment in a moisture-vapor
proof barrier with a quantity of desiccant placed
around the recorders. Heat-seal the barrier.
c. Place the equipment in a cool, dry place.
Section II. DEMOLITION TO PREVENT ENEMY USE
64. Methods of Demolition b. Cut. Use axes, handaxes, machetes.
c. Burn. Use gasoline, kerosene, oil, flame
a. Smash. Use sledges, axes, handaxes, pick- throwers, incendiary grenades,
axes, hammers, crowbars, heavy tools. d. Explode. Use firearms, grenades, TNT.
C-5I E-6 T-4 T-8
R-78 £-t3 V-l V-4 V-7 V-6 V-9 V-ll
Figure 50. Recorder BC-1S2S-A, tape guard and end cover removed.
TM255ZA-47
52
PROTECTIVE
COVER
.CAPTIVE
CHAIN
STAKE.
STOP-
RUBBER
WASHER '
MICROPHONE
ELEMENT
Figure 51. Microphone T-56, exploded view.
e. Dispose. Bury in slit trenches, fox holes,
other holes. Throw in streams. Scatter.
/. Other.
Note. Use anything immediately available for de
struction of this equipment.
65. Destruction of Components
When ordered by the commander, destroy all
equipment to prevent its being used or salvaged
by the enemy.
a. Smash the recorder, power unit, radio set,
all headsets and handsets, and batteries.
b. Cut all wires, cables, and computers.
c. Burn all technical manuals, circuit dia
grams, etc.
d. Bury or scatter all remaining parts of the
equipment.
e. Destroy everything.
54
APPENDIX I
REFERENCES
Note. For availability of items listed, check SR 310-20-3 and SR 310-20-4.
1. Technical, Administrative, and Supply Publications
SB 11-47
SR 310-20-3
SR 310-20-4
SR 700-45-5
SR 745-45-5
TM 1-455
TM 9-2820
TM 9-2857
TM 11-453
TM 11-455
TM 11-2250
TM 11-242
TM 11-4302
AR 750-5
SB 11-76
TB SIG 13
TB SIG 66
TB SIG 75
TB SIG 123
Preparation and Submission of Requisitions for Signal Corps Supplies.
Index of Training Publications (Field Manuals, Training Circulars, Firing
Tables and Charts, Army Training Programs, Mobilization Training
Programs, Graphic Training Aids, Joint Army-Navy-Air Force Publica
tions and Combined Communications Board Publications) .
Index of Technical Manuals, Technical Regulations, Technical Bulletins,
Supply Bulletins, Lubrication Orders, Modification Work Orders, Tables
of Organization and Equipment, Reduction Tables, Tables of Allowances,
Tables of Organization, and Tables of Equipment.
Unsatisfactory Equipment Report (Reports Control Symbol CSGLD-247).
Report of Damaged or Improper Shipment (Reports Control Symbols
CSGLD-66) .
Electrical Fundamentals.
Shop Mathematics.
Storage Batteries Lead-Acid Type.
Shop Work.
Radio Fundamentals.
Reel Equipment CE-11
Radio Set SCR-300-A
Tactical Switchboards and Long Lines Equipment—Repair Instructions,
Apparatus Requirements.
Maintenance Responsibilities and Shop Operation.
Signal Corps Kit and Materials for Moisture- and Fungi-Resistant Treat
ment.
Moistureproofing and Fungiproofing Signal Corps Equipment.
Winter Maintenance of Signal Equipment.
Desert Maintenance of Ground Signal Equipment.
Preventive Maintenance Practices for Ground Signal Equipment.
2. Packaging and Packing Instructions
a. Joint Army-Navy Packaging Specifications.
JAN-D-169 Desiccants (Activated).
JAN-P-100 Packaging and packing for overseas shipment—General specification.
JAN-P-106A Packaging and packing for overseas shipment—Boxes, wood, nailed.
JAN-P-116 Packaging and packing for overseas shipment—Preservation, methods of.
JAN-P-125 Packaging and packing for overseas shipment—Barrier-materials, water
proof, flexible.
JAN-P-131 Packaging and packing for overseas shipment—Barrier-material, moisture-
vaporproof, flexible.
55
CAPACITOR COLOR CODES
RMA 3-jt-5-A6-D0T COLOR CODES FOR
MICA-DIELECTRIC CAPACITORS
f4■ 20 ISIONi
. IST/ fig
MULTIPLYINGVALUEJIFICANTIGURES
3-DOT COLOR CODING
(SOO VOCW t 20%)
-TOLERANCE
9 9 9
MULTIPLYING*~ VALUE
20 \siGNIFICANTI IST/ FIGURES
4-DOT COLOR CODING
(900 VOCW)
B
-WORKING VOLTAGE-TOLERANCE
MULTIPLYINGVALUE
20l SIGNIFICANTIST/ FIGURES
1=11=3
I—TOLERANCE
-WORKING VOLTAGE
REAR 5-DOT COLOR COOING
-TOLERANCE-LEFT BLANK
I WORKING VOLTAGE
21
ft
ft
—TOLERANt
IsiGNi
F"
IIFICANTIGURES
MULTIPLYINGVALUE
-TOLERANCE
-WORKING VOLTAGE (OR ICHARACTERISTIC)
RMA COLOR CODE FOR TUBULAR
CERAMIC-DIELECTRIC CAPACITORS
TEMP COEFFICIENT
TOLERANCE
MULTIPLYING VALUE
(900 VDCW)
JAN 6-DOT COLOR CODES FOR:
PAPER-DIELECTRIC CAPACITORS *
-this dot is always silver
ist\significant3/ FIGURES
MULTIPLYINGVALUE
I—TOLERANCE
CHARACTERISTIC
MICA-DIELECTRIC CAPACITORS11
r-THIS COT IS ALWAYS BLACK
t 0
o o
4
IST V SIGNIFICANT2„/ FIOU&S
MULTIPLYINGVALUE
-TOLERANCE
-CHARACTERISTIC
D E
COLORSIGNIFICANT
FIGURE RMA MICA- ANDCERAMIC-DIELECTRIC
MULTIPLYING VALUE
JAN MICA-ANDPAPER-DIELECTRIC
JAN CERAMIC-DIELECTRIC
VOLTAGERATING
RMA
BLACKBROWNRED
0 I I II0
I00LOCO
I0,000lOOjOOO
LOO0,000I0,000,000
I0I00
LOOOIOJWO
I0I00IpOO
I00
tooORANGE 300
400500(00
YELLOWGREENBLUEVIOLET 700
SOOGRAY ioojooo,qoo 00I0IWHITE U300000,000
0I00I
900LOOO2000SOO
GOLD 0I00ISILVER
NO COLOR
CERAMIC-DIELECTRIC CAPACITORS **
-TEMPERATURE COEFFICIENT
-IStV SIGNIFICANTFIGURES
TEMPERATURE~ COEFFICIENT
H
NOTES
* THE SILVER DOT IDENTIFIES THIS MARKINGFOR WORKING VOLTAGES SEE JAN TYPEDESIGNATION COOE.
THE BLACK DOT IDENTIFIES THIS MARKING.FOR WORKING VOLTAGES SEE JAN TYPEDESIGNATION CODE.
Kit CAPACITORS MARKED WITH THIS COOE HAVEA VOLTAGE RATING OF SOO VDCW. EITHERTHE BAND OR DOT CODE MAY BE USED FORBOTH INSULATED IAXIAL-LEADI OR UNINSULATED IRAOIAL-LEAO) CAPACITORS.
RMA RAOIO MANUFACTURERS ASSOCIATION
JAN: JOINT ARMY-NAVY
THESE COLOR COOES GIVE CAPACITANCES INMICROMICROFARADS.
TL32433S
Figure 52. Capacitor color codes.
56
b. U. S. Army Specifications.
100-2E
100-14A
Marking Shipments by Contractors (and Signal Corps Supplement thereto) .
Army-Navy General Specification for Packaging and Packing for Overseas
Shipment.
c. Signal Corps Instructions.
720-7 Standard Pack.
726-15 Interior Marking.
RESISTOR COLOR CODES
RMA COLOR CODE FOR
FIXED COMPOSITION RESISTORS*
JAN COLOR CODE FOR
FIXED COMPOSITION RESISTORS'*
IST 1 SIGNIFICANT
20 I FIGURES
TOLERANCE
MULTIPLYING VALUE
METHOD A
(BODY)• lST\siGNIFICANT
FIGURES
-MULTIPLYING VALUE
METHOD B
r
SIGNIFICANTFIGURES
111
CZI i
COLORSIGNIFICANT
FIGUREMULTIPLYING
VALUE TOLERANCE (%)
BLACK 0
I
I ¥ _
I0 t I
RED 2 I00 i 2
ORANGE 3 I,000 t 3
YELLOW * IOjOOO t 4
GREEN 5 I00,000 t 5
BLUE 6 I.000,000 t «
yiOLET 7 I0,000,000 ♦ 7
GRAY 8 loopoo.ooot 8
WHITE 9 ipoo.ooo.ooo t s
GOLD — 0 I + 5
SILVER - 00t t I0
NO COLOR — —i 20
*— TOLERANCE
MULTIPLYING VALUE
METHOD A
-TOLERANCE
,— MULTIPLYING VALUE
CD
METHOD B
BODY) L2D\SIGNIFICANT
IST/ figures
B
NOTES
INSULATED FIXED COMPOSITION RESISTORSWITH AXIAL LEAOS ARE DESIGNATED BY
A NATURAL TAN BACKGROUND COLORNON-INSULATED FIXED COMPOSITION RESISTORS WITH AXIAL LEADS ARE DESIGNATED BY A BLACK BACKGROUND.
r RESISTORS WITH AXIAL LEADS ARE IN--
SULATEO. RESISTORS WITH RADIAL LEADSARE NON-INSULATED.
RMA RADIO MANUFACTURERS ASSOCIATION-
JAN JOINT ARMY-NAVY
THESE COLOR COOES GIVE ALL RESISTANCE
VALUES IN OHMS
TL32454S
Figure 53. Resistor color codes.
57
APPENDIX II
IDENTIFICATION TABLE OF PARTS
Note. The fact that a part is listed in this table is not sufficient basis for requisitioning the item. Requisi
tions must cite a T/O & E, T/A, SIG 7 & 8, SIG 7-8-10, SIG 10, list of allowances of expendable material, or
other authorized supply basis. The Department of the Army Supply Catalogs applicable to the equipment covered
in this manual are SIG 7 GR-6 and SIG 8 GR-6. For an index of available supply catalogs in the Signal portion
of the Department of the Army Supply Catalog, see the latest issue of SIG 1.
Name of part and description
MISCELLANEOUS ITEMS GROUP
BAG BG-44: tool; cotton duck; olive drab; water
repellent.
BAG BG-160-A: general purpose; blk rubberized
nylon; watertight.
BAG BG-182-A: carrying; blk rubberized nylon;
watertight.
BATTERY, Box CH-291: aluminum; 3 compart
ments.
BATTERY BB-221/U, storage: portable; 3 cells; 6
v; 120 amp-hr.
BATTERY BB-54-A, storage: 2 v
BOARD, plotting: portable; plastic (Plotting Board
M-10).
BOX: CH-318: plywood, olive-drab finish; single
compartment.
CAP, battery: p/o Battery BB-221/U; hard rubber..
CAP, battery: p/o Battery BB-54-A; bakelite
CASE CS-148: cotton duck; circular
CASE CS-161: aluminum; olive-drab finish; 6 com
partments.
CHAIN M-457: bead type #13; brass; 15 ft. lg.._
CHAIN M-458: bead type #13; brass; 21 ft. 214
in. lg.
CLAMP: Cable Clamp M-284; aluminum; fits cable
w/J/£ in. max dia.
CLIPBOARD: Holder M-167-A
COMPASS, magnetic: moving needle (Ordnance
Compass M-2).
COMPUTOR M^14, azimuth: phenolic, circular
CONNECTOR, plug: 5 round male contacts; type
AN3106-14S-5P.
CONNECTOR, plug: 7 round female contacts; type
AN3106-16S-1S.
CONNECTOR, plug: 3 round male contacts; type
AN3106-14S-7P.
CONNECTOR, receptacle: 5 round female con
tacts; type AN3101-14S-5S.
CONNECTOR, receptacle: 3 round female con
tacts; type AN3102-14S-7S.
Function of part
Tool container
Microphone and cable container....
Carrying case for Recorder
BC-1323-A.
Container for Battery BB-54
Furnishes 6 volts
Furnishes 2 volts
Computing device
Holds Battery BB-221/U
Cover for battery cell
Cover for battery cell
Holds Computer M-414 _
Holds running spare parts and
other components of Sound Lo
cating Set GR-6A.
Fixes microphone array position-
Fixes microphone array position ....
Secures cable connector
Holds data sheets
Determines bearing
Determines range and azimuth
Connects to radio receptacle PI
Battery cable connector
J201—Battery box receptacle; re
ceives P101.
J301—Receptacle on Battery Box
CH-318.
Signal Corpsstock Xo.
6Q2044
2Z551-160A
2Z551-182A
3B380-291
3B275-221
3B54
6Z1006-7
3B901-318
3B695-1
3B695
4G330-148
6F461
6Z1806A-3
6Z1806A-4
2Z1587-284
6M567
6Z2203-4
4G370-414
22K7115.4
2Z8677.14
2Z71 13.35
2Z3066-17
2Z3064-8
58
Identification Table of Parts—Continued
Ref symbol Name of part and description Function of partSignal Corpsstock No.
P201
J101
P103, PI 04,
P105, P106,
P107
P109, PI 10
P108, Pi11,
P112
S101
CONNECTOR, receptacle: 3 round male contacts;
type AN3102-14S-7P.
MARKER MC-693: luminous; phenolic.
MICROPHONE T-56: 225-ohm impedance; e/o
housing, sound-powered microphone unit, cover
assembly, plug, cap, spring washer, and rubber
gasket.
CORD AND CABLE GROUP
CABLE ASSEMBLY, power: Cord CD-1446, Cord
age CO-132; 6 ft lg.
CABLE ASSEMBLY, power: electrical; Cord
CD-1240, Cordage CO-132; 15 ft lg.
CABLE ASSEMBLY, special purpose: Cord
CD-1239, Cordage CO-132; 50 ft lg.
CABLE ASSEMBLY, special purpose: electrical;
Cord CD-1444; 5 ft 2 in. lg.
CONNECTOR, plug: 5 round female contacts; type
AN3106-14S-5S.
CONNECTOR, plug: 5 round male contacts; type
AN3106-14S-5P.
CORD, headset: Cord CD-874; 614 ft lg—
CORD, microphone: Cord CD-1238-A; 3 ft of Cord
age CO-132 and three 15 ft lengths of #18 AWG
cond.
GROMMET: rubber...
INSULATION, flexible sleeve : blk ; plastic extrusion..
LEAD, electrical: \Yt ft lg...
Part of CH-291; connects to bat
tery charger.
Marks microphone position
Converts sound energy into elec
trical energy.
Connects battery box to recorder...
Connects stop switch to recorder
Connects recorder to microphone
array.
Connects radio set to recorder
Connects to 6-volt battery recept
acle P2.
P103—Connects to microphone re
ceptacle J1.
P104, P105, P106—Connect to
microphones No. 1, 2, and 3,
respectively.
P107—Connects to J4.
Connects headset to recorder
Connects microphone to Cord
CD-1239.
PLUG, telephone: tubular; blk bakelite; 3 cond,
1 shank.
PLUG, telephone: tubular; blk bakelite; 2 cond, 1
shank; JAN type PJ-055-B.
SLEEVE, cord: neoprene; p/o Cord CD-874..
SWITCH, push-pull
To connect handset..
To connect phones, relay, and
microphone.
Starts and stops recorder tape
movement.
MISCELLANEOUS TOOLS AND
SUPPLIES GROUP
ABRASIVE, sheet: sandpaper, #00 flint; 6 sheets
per unit.
BRUSH TL-72, painting: camel's hair
CARBON TETRACHLORIDE: technical grade...
CEMENT, liquid: general purpose
DRILL, star: carbon steel; straight shank; K-in. dia...
FLUX, soldering: acid paste
FUNNEL: blk plastic
HAMMER, hand: ball peen; #4, 2 lb...
NOTEBOOK: cross section; quadrille, 10 divisions
to the in.
OIL, lubricating: low temp; for light mechanical
parts.
PENCIL: blk #2 lead
PLIERS TL-304/U: long-nosed w/cutters
PLIERS: needle-nosed
SCREW DRIVER: offset; 2 blades ea J£ in. lg,
perpendicular to shank.
2Z3023-5
2Z6502-693
2B1656
3E 199-446
3E1999-240
3E1999-239
3E1999-444
2Z7226-P200
2ZK7115.4
3E1874
3E1999-238A
6Z4853-8
3G2425-1
3E7998-4.6
2Z7168
2Z7228A-55B
2Z8552-19
3Z9815-12
6Z7500-00.1
6Z1372
6G184.1
6G202.11
6Q35208-12
6N4102
6Z4028-4
6Q49732
6M676-1
6G1398.7
6R4512X
6R4602A
6R1833-3
59
Identification Table of Parts—Continued
Ref symbol Name of part and description Function of partSiena 1 Corpsstock No.
S101
J401
E7
E8
E9
E10
E11
E12
E13
E14, E16, E17
E15
E18, E19
C46A, C46B,
C46C, C48A,
C48B, C48C
C3, C5, C13,
C15, C23,
C25, C31,
C32, C33,
C37, C43
C49, C50
C2, C4, C8,
C12, C14,
C18, C19,
C22
C24, C28, C29,
C38, C44,
C47
C45A, C45B
C52
C6, C16, C26
C40
CI, C11, C21
C7, CI 7, C27,
C34, C35
CIO, C20, C30,
C41
SCREWDRIVER: offset; 4 in. blade
SCREW DRIVER: TL-458/U straight; 5lA in.
blade.
MICROPHONE T-56 GROUP
CONNECTOR, receptacle: 5 contacts
GASKET: rubber
MICROPHONE: sound-powered, element
SHELTER: microphone (Microphone Shelter
M-413).
WASHER, spring
RECORDER BC-1323-A GROUP
ABSORBER, shock
BLOCK, bearing: aluminum
BLOCK, bearing: aluminum
BOARD, terminal: 12 lugs
BOARD, terminal: 4 lugs
BOARD, terminal: 11 terminals
BOARD, terminal: 38 turret lug terminals and 9 lugs.
BOARD, terminal: 9 terminals
BOARD, terminal: 2 TM-175 terminals
BOARD, terminal: 2 turret lug terminals
BOARD, terminal: 4 lug terminals—
BOARD, terminal: 2 lug terminals..
BOARD, terminal: 2 terminals
BRUSH: carbon and copper; input-
BRUSH: carbon; output
CAPACITOR: electrolytic; 3 section; 600 vdcw;
15-15-15 ni.
CAPACITOR: paper; 600 vdcw; 10,000 wif_
CAPACITOR: paper; 400 vdcw; 20,000 «if....
CAPACITOR: paper; 600 vdcw; 100,000 wif_
CAPACITOR: paper; 600 vdcw; 100,000 «if_„
CAPACITOR
250,000 wif
CAPACITOR
CAPACITOR
CAPACITOR
CAPACITOR
CAPACITOR
paper; 2 section; 600 vdcw;
paper; 100 vdcw; 1/xf
mica; 400 vdcw; 500 «»f._
mica; 500 vdcw; 560 niti..
mica; 400 vdcw; 1000 «i£.
mica; 500 vdcw; 1000 wif.
CAPACITOR: mica; 500 vdcw; 2000 wif.
Provides connection with Cord
CD-1238.
Provides seat for microphone cover
Converts sound into electrical
energy.
Shelters microphone from extran
eous noises.
Provides tension against micro
phone element.
Absorbs vibration and shock
Supports scanning wheel
Supports driving head
Provides terminals for wires
Same as E7
Same as E7
Provides terminals for resistors
and capacitors.
General purpose.
Line terminal panel..
Mounts pip circuit components
Magnetic head terminal strip
Magnetic head terminal strip
Capacitor terminal plate.
Provides contact to commutator
on dynamotor.
Same as above
Filter
C3, C5, C13, C15, C23, C25—
Plate coupling.
C31, C32, C33, C37—Coupling.
C43—Voltage doubler.
Bypass high frequency
C2, C4, C8, C12, C14, C18, C22—
Bypass screen and B plus.
C9, C19—Output coupling.
C-24, C-28—Bypass screen and
B plus.
C29—Output coupling.
C38—Cathode bypass.
C44—Blocking.
C47—High voltage bypass.
Blocking
Coupling
Grid bypass..
Plate load
Grid bypass
C7, C17, C27—Plate bypass.
C34, C35—Coupling.
C10, C20, C30—Coupling.
C41—Feedback.
6R18334-3
6R15811
2Z3066-17
2Z4868.733
2B1717-5
2B2165-413
6L73628-1N
2Z142-5
6C9E-2
6C9E-1
2Z9412.107
2Z9464.2
2Z9411 . 15
3Z770-38.9
2ZK9409.6
3Z770-2.76
3Z770-3.43
3Z770-8.65
2Z9402.236
3Z770-2.67
3H525C-5
3H525-34
3DB15-64
3DA10-388
3DA20-156
3DA100-730
3DA100-730
3DA250-415
3DBI-195
3D9500-236
3K2556121
3DA1-290
3K3010222
3K3020222
60
Identification Table of Parts—Continued
Ref symbol Name of part and description Function of part
Oscillator tuning
C36—Coupling
C39—Screen bypass.
Coupling..
Starts and stops tape motion
L5—Generates pick-up voltage.
L6, L8, L11—Apply erasing volt
age to tape.
L7, L10—Generate recorder repro
ducer voltage.
L9—Applies pip signal voltage to
tape.
Core for clutch 0-2
Provides radio connection
Provides battery connection
J1—Provides microphone connec
tion.
J4—Provides stop-switch connec
tion.
Indicates position of tape
Same as 1-3
Moves tape manually
Supplies B voltage
Cushions switch leaf
Cleans recording tape
Protects against overload.-
Same as F3
Seals cover and door
Operates mechanical counter
Same as above
Same as above
Protects recording tape
Alines tape
Varies position of magnetic head...
Holds fuse cartridge
Same as E5
Connects radio headset to equip
ment.
Connects radio handset to equip
ment.
Same as J3
Used to rotate dials._.
Same as above
Generates pip signal
Illuminate panel
Support lamp E1-
Supports lamp E6
Supports Recorder BC-1323-A
Absorbs vibration
Same as above
Provides leverage for turning screw
E21, E25, E29, E31—Movable
recorder head pole piece.
E23, E27, E33—Movable erase
head pole piece.
E20, E24, E28, E30—Stationary
recorder head pole piece.
E22, E26, E32—Stationary erase
head pole piece.
Signal Corpsstock No.
C51
0-2
L5, L6, L7, L8,
L9, L10, L11
E21, E23, E25,
E27, E29,
E31, E33
E20, E21, E24,
E26, E28,
E30, E32
CAPACITOR: mica; 500 vdcw; 3000 n/J
CAPACITOR: mica; 500 vdcw; 5600 MMf
CAPACITOR, fixed: paper; 600 vdcw; 20,000 «i£..
CLUTCH, magnetic
COIL, reproducer head
COIL, solenoid _
CONNECTOR: receptacle; 7 contact..
CONNECTOR: receptacle; 5 contact.
CONNECTOR: receptacle; 5 contact; female..
COUNTER, mechanical
COUNTER, mechanical
DIAL: scanning wheel
DYNAMOTOR: 250 v. DC output, 30 ma. .
FELT
FELT: recording tape
FUSE, cartridge: % amp, 250v
FUSE, cartridge: 6 amp, 250 v
GASKET: rubber; rectangular-shaped
GEAR: bevel type; 18 teeth
GEAR: spur type; 54 teeth..
GEAR: Spur type; 14 teeth
GUARD : tape, aluminum
GUIDE, tape..
HEAD, micrometer
FUSEHOLDER: 10 amp; retainer type
FUSEHOLDER: 10 amp; retainer type..
JACK, telephone: 2 cond
JACK, telephone: 2 cond..
JACK, telephone: type JK-33-C.—
KNOB: blk plastic
KNOB: blk phenolic; round
LAMP, glow: 105 to 125 v., 1/25 w
LAMP, incandescent (Lamp LM-52): 6 to 8 v..
LAMPHOLDER...
LAMPHOLDER—
LEG: telescopic tubes; aluminum
MOUNT, vibration: oval mounting
MOUNT, vibration: square mounting
NUT, thumb: aluminum; #6-32 NC-2
POLE PIECE: permalloy.—
POLE PIECE: recorder head; permalloy..
3K3030222
3K3556221
3DDA20-208
6C13C-4
6C171-1
3C1999-31 A
2Z3027-18
2Z8799-180
2ZK7409-20
6Z3417-43
6Z3417-44
2Z3723-202
3H1506-10
6Z3812-4
6Z3812-5
3Z2585.1
3Z2606.3
6Z4182-2
2Z4878-1147
2Z4878-1146
2Z4878-1148
6C25F
6C25J-4
6C26A-2
3Z3282-29
3Z3282-29.2
2Z5534
2Z5598-31
2Z5533C
2Z5822-435
2Z5842-12
2Z5952
2Z5956.27
2Z5956.28
6C33-3
2Z8405-85
2Z8402-10
6L2506-32-4
6C180
6C180-1
61
Identification Table of Parts—Continued
Ref symbol Name of part and description
POST, binding: TM-175-
PULLEY: tape tension
PULLEY ASSEMBLY: driven tape.
PULLEY ASSEMBLY: driving
REACTOR: audio; 0.1 hy
REACTOR: audio; 200 hy/50 hy
RECTIFIER, metallic: selenium.
REDUCER, speed
RELAY, armature: SPST
RESISTOR, fixed: 100 ohms, ^ w
RESISTOR, fixed: 2,000 ohms, Yi w..
RESISTOR, fixed: 2400 ohms, lA w...
RESISTOR, fixed: 3600 ohms, Yi w...
RESISTOR, fixed: 5600 ohms, Yi w...
RESISTOR, fixed: 6800 ohms, Y w...
RESISTOR, fixed: 10,000 ohms, 1 w.._
RESISTOR, fixed: 15,000 ohms, Yt w..
Function of part
Provide terminals for wire (line
terminal posts).
Permits tape tension adjustment ..
Driven tape pulley
Driving tape pulley..._
LI—Filter.
L2—High voltage step-up.
Part of band-pass circuit
Convert ac to dc
Reduces D1 speed for tape motion .
Operates clutch O-2
Voltage dropping -
Cathode bias..._
Voltage dropping
Cathode bias..
Voltage dropping
Cathode bias.-
Voltage dropping
Attenuator section
Attenuator section
Attenuator section
R19, R39, R59—Plate load.
R65—Isolation resistor.
R7, R27, R47—Attenuator section.
R72—Grid leak.
Current limiting
Attenuator section._
Screen dropping
R3, R14, R23, R34, R43, R54—
Plate loading.
R5, R25, R45—Attenuator section.
R16, R36, R56—Low-pass filter.
R69—Grid leak.
R1, R21, R41—Low-pass filter.
R15, R35, R55—Grid leak.
R61—Vertical deflection plate low-
pass filter.
R62—Vertical deflection plate
loading.
R63—Horizontal deflection plate
low-pass filter.
R64—Horizontal deflection plate
load.
R4, R13, R24, R33, R44, R53—
Screen dropping.
R78—Controls pip frequency.
Intensity control
Focus control
Holds fixed and movable magnetic
poles at pivot points.
Extends attenuator shaft-
Shields eye from light
Signal Corpsstock No.
E35, E36
0-3
L1, L2
L3
CR1, CR2
O-1
R76
R17, R37, R57
R73, R74, R75
R70
R67
R2, R12, R22,
R32, R42,
R52
R77
R10, RU, R30,
R31, R50,
R51
R9, R29, R49
R8, R28, R48
R19, R39, R59,
R65
R7, R27, R47,
R72
R20, R40, R60
R6, R26, R46
R18, R38, R58,
R71
R3, R5, R14,
R23, R25,
R34, R43,
R45, R54
R16, R36, R56,
R69
R1, R15, R21,
R35, R41,
R55, R61,
R62, R63,
R64
R4, R13, R24,
R33, R44,
R53, R78
R66
R68
RESISTOR, fixed:
RESISTOR, fixed:
RESISTOR, fixed:
30,000 ohms, Yi w....
62,000 ohms, Yi w....
100,000 ohms, Yt w..
RESISTOR, fixed: 120,000 ohms, Yi w
RESISTOR, fixed:
RESISTOR, fixed:
RESISTOR, fixed:
220,000 ohms, Yi w..
240,000 ohms, Yi w..
270,000 ohms, Yi w..
RESISTOR, fixed: 470,000 ohms, Yt w.._
RESISTOR, fixed: 470,000 ohms, Yi w.._
RESISTOR, fixed: 1 megohm, Yz w _
RESISTOR, fixed: 1.8jnegohm, Yi w..
RESISTOR, variable: 25,000 ohms, 2 w.._
RESISTOR, variable: 100,000 ohms, 2 w
SCREW, adjustment: slot drive; brass, nickel pi;
#3-56 thread.
SCREW, machine: slot drive; stainless steel; #4-40
thread.
SHAFT: aluminum, anodized; 14 in- dia x 5% in. lg.
SHIELD, light: synthetic neoprene —
3Z275
6C255-11
6C255-13
6C255-12
3C573-37
3C573-36
3H4860-128
6C274A
2Z7585-197
3RC20BF101J
3RC20BF202J
3RC20BF242
3RC20BF363J
3RC20BF562J
3RC20BF682J
3RC303F103K
3RC20BF153J
3RC20BF303J
3RC20BF623J
3RC20BF104J
3RC30BF124J
3RC20BF224J
3RC20BF244J
3RC2013F274J
3RC20BF474J
3RC20BF474J
3RC20BF105J
3RC20BF185J
3RV42503
3RV51004
6L4713-2N
6L20904-10.3F
2Z8204-172
6C2790-1
62
Identification Table of Parts—Continued
Ref symbol Name of part and description Function of part
Shields reproducer head.
Shields tube 6AK6
Shields t ube 9001
Support tube
Supports cathode-ray tube
Provides compression in tube shield.
Provides tension against tape..
Carrying strap for Recorder
BC-1323-A.
Reverse blanking switch
Signal Corpsstock No.
K34
X1, X2, X3,
X4, X5, X6,
X7, X8, X9,
X10, Xl1
X12
SO
SI
S2
S3
S5A, S5B, S5C
84
S7
Tl, T2, T3,
T4, T5, TO,
T7
V12
V1, V2, V3,
V4, V5, VG,
V7, V8, V9,
V10
V11
SHIELD, reproducer head: zinc pi and iridited
SHIELD, tube: brass, nickel pi; cylindrical; bayonet
mounting; JAN type TSFOT102.
SHIELDS, tube: cylindrical, w/J<j in. dia hole in
top; bayonet mounting; JAN type TSFOT101.
SOCKET, tube: 7 contacts, miniature; JAN type
TSE7T101.
SOCKET, tube: 11 contacts
SPRING: helical compression type; stainless
wire; 5 turns.
SPRING: helical tension type; stainless steel wire
STRAP, carrying: olive-drab cotton webbing
teel
SWITCH ASSEMBLY: c/o bracket and leaf assem
bly, block assembly, and insulating spacer.
SWITCH, lever: 2 position locking; metal body
SWITCH, lever: 2 position locking; metal body
SWITCH, push: SPST; silver contacts _
SWITCH, rotary: 6 pole; 7 positions; 3-section
SWITCH, toggle: DPDT; JAN type ST52P
SWITCH, toggle: DPST; JAN type ST52K
TAPE, blank recording: .050 in. ±.002 in. wd x
.002 in. ± .0002 in. thk.
TRANSFORMER, AF: input type; primary
125/200/500 ohms impedance; secondary 50,000
ohms impedance; hermetically sealed.
TUBE, electron: electrostatic deflection; type
2AP1-A.
TUBE, electron: pentode; type 9001-
TUBE, electron: pentode; miniature type; 6AKS ...
WASHER, flat: round; 5/32 in. ID, 9/32 in. OD
WIPER, tape: brass, cad pi
WRENCH: L shaped; steel, cad pi; special for #0
set screw.
Main control lcver._
Play-back switch
Pilot lamp switch
Volume control
RADIO SURVEY OFF switch
Power switch
Recording and play-back medium.
Transfer electrical energy by mu
tual conduction.
Cathode-ray tube..
Amplifier tube
Oscillator tube .
Knob set screw wrench
2Z8320-13
2Z8304.57
2Z8077.94
2Z8081 . 19
2Z8877.339
2Z8877.338
2Z9052-104
3Z9824-104
3Z9580-30.25
3Z9580-30.24
3Z9824-2.1
3Z9825-02.519
3Z9863-52P
3Z9803-52K
6C303-2
2Z963 1.391
2J2AP1A
2J9001
2J6AKS
6L54002-13
6C578
6R55230
63
INDEX
Paragraph Page
Accelerator pin, cathode-ray tube 516 42
Amplifier :
Channels 46a 37
Headset 8a, 47 4,40
Isolation 47 40
Microphone 8a 4
Specific faults and remedies 56 44
Amplitude errors 456 36
Arm, computor 326(4) 27
Arrays 23a 17
Attenuation :
High-frequency 516 42
Steps 466 37
Audio:
Frequency oscillator 48 40
Stage gain chart 57 45
Azimuth:
And range of target 36e 32
Angle error 32c 27
Bag BG-44 12 H
Bag BG-160A 10 5
Bag BG-182A 9 5
Base line 23a 17
Distance and azimuth 35 30
Battery BB-54 15 12
Battery BB-221/U - - - ■ - 16 12
Battery Box CH-291 15 12
Battery Box CH-318 16 12
Bias and erase oscillator 8a 4
Blanking switch 47 40
Brush:
Holder 61; 50
Lead wire 61flr 50
Case CS-161 H ?
Cathode coupling 47a 40
Cathode-ray tube 8a, 55 4, 44
Biasing 47c 40
Grid-to-cathode potential 51a 41
Chain M-457 10/ '
Chain M-458 10/ 7
Characteristics, technical 4 1
Chart, trouble-shooting 59 46
Computing:
Distance 33c 29
Process 45c 37
Computor 11c, 326 8,26
Arm 326(4) 27
Controls :
FOCUS 216,51a 16,41
Front panel 20 14
INTENSITY 21c, 51a 16,41
Side panel 21a 16
VOLUME 20a 14
Cord CD-1238-A 10c 5
INDEX
Paragraph Page
Cord CD-1239 10d 6
Cord CD-1240 10c 5
Cord CD-1446 Hrf 9
Correction factor 24 17
Counter adjustment knobs 20c 14
DA AGO Form 419 2c 1
DA AGO Form 468 26 1
Data, packaging 7 3
DD Form 6 2o 1
Definition of preventive maintenance 40 33
Deflection plates 456 36
Destruction of components 65 54
Distance and azimuth:
Base line 35 30
Computing 34c 30
Recheck 34d 30
Dynamotor 44a 36
Replacing brushes 61 49
Equipment:
Performance checklist 27 23
Required 6 3
Supplied 5 2
Erase head 44a 36
Errors:
Amplitude 456 36
Phase 456 36
Extinction voltage 496 41
Field maintenance 43 36
Filter, low-pass 466 37
Finding distance 33a 28
Azimuth angles, using radio 34 29
FOCUS control 8c, 216, 51a 4,16,41
Forms 2 1
Frequency :
Lubrication 41d 34
Response 46a, 466 37
Front panel controls 20 14
Glow discharge 496 41
Guides, sapphires 606(5) 48
Handset H« 8
Head:
Pip signal 44a 36
Recorder-reproducer 44a 36
Headset H6 8
Amplifier 47 40
Heater voltage 50a 41
High-frequency attenuation 516 42
Ignition voltage 496 41
Initial adjustment 26 21
Input transformer 45a 36
INTENSITY control 8c, 21c 4, 16
Interconnecting equipment 26 21
Operation:
Radio 26c 22
Wire-line 266 22
65
INDEX
Paragraph Page
Laying-off CB-R azimuth 36a 31
Lever :
Main control 20(2 15
Play-back 20a 14
Lubricating details 41/ 34
Counter assemblies 41/(2) 34
Hinges 41/(1) 34
Magnetic tape, pole pieces 41/(3) 34
Scanning wheel 41/(4) 35
Lubrication 42c 35
General 41a 34
Magnetic :
Clutch 44a 36
Steel tape 44a, 446 36
Main control lever 86, 20d, 32a(2) 4,15,25
Maintenance:
Desert 42d 35
Tropical 426 35
Winter 42c 35
Marker He 9
Measurement of voltage and resistance 58 45
Methods of demolition 64 52
Microphone 10a 5
Amplifier 8a 4
Monitoring 46c 38
Shelter 86 4
Multimeter TS-297/U 13 11
Muzzle blast 32a(7) 25
Operation :
Climate :
Arctic 29 24
Desert 30 25
Tropical 31 25
Oscillator:
Peak voltage 506 41
Relaxation 49a 41
Tank circuit 506 41
Oscilloscope 456 37
Output transformer 45a 37
Packaging data ' 3
Packing equipment for shipment 62 52
Parts, spares 1? 12
Pattern, scope 32a (17) 26
Performing preventive maintenance 40 33
Phase :
Errors 456 36
Shift 46a 37
Pip:
Head 49a 41
Signal 49 41
Plate load resistor 46c 38
Plates, deflection 456 36
Play-back :
Lever 20c 14
Process 456 36
Plotting:
Azimuth from arrav to target 36d 32
Board 11/, 36, 45c 11,31,37
INDEX
Paragraph Page
Plotting :—Continued
Position :
Left array 36c 32
Right array 366 31
Power :
ON-OFF switch 8c, 21 4,16
Requirements 53 43
Supply 50 41
Prerepair procedures, general 52 42
Preventive maintenance :
Daily 40a 33
Monthly 406 33
Performing 40 33
Quarterly 40c 33
Push-button switch 86, 20/ 4,15
Radio method . 356 30
SURVEY—RADIO—OFF switch 8c, 21d 4, 16
Rear panel 8d 5
Recheck distance and azimuth 34d 30
Recorder 8 4
Mechanism 44 36
Opening and removing covers 54 43
Reproducer head 44 36
Recording process 45a 36
Rectifier, selenium 506 41
Reel Equipment CE-11 14, 266(5) 11,22
Reflected impedance 46c 38
Relaxation oscillator 49a 41
Removing and replacing magnetic tape 60 48
Repacking for limited storage 63 52
Sapphire guides 606 (5) 48
Scanning wheel 206, 32a(14), 44a 14,25,36
Scope pattern ' 32a (17) 26
Selecting site 23, 25 17, 21
Selenium rectifier 506 41
Service upon receipt of equipment:
General 18 14
Unpacking 19 14
Setting up array 22,24 17
Side panel controls 21 16
Signal-to-noise ratio 48 40
Solvent, dry-cleaning (SD) 406 33
Sound :
Blast 45 36
Locating set 3 1
Wave 456 36
Spare parts 17 12
Specific faults and remedies 56 44
Amplifiers 566 45
Magnetic tape control 56a 44
Speed number, use 32d 28
Stop button switch 8, 21e 4,17
Straight-line scope pattern 456 36
Summary of complete procedure 37 32
SURVEY—RADIO—OFF Switch 8c,21rf 4,16
Surveying with plotting board 36 31
Switch :
Blanking 47 40
Power ON-OFF 21 16
INDEX
Paragraph Page
Switch :—Continued
Push-button 86,20/ 4,15
SURVEY—RADIO—OFF 8c, 2ld 4,16
Tank circuit, oscillator 506 41
Tape:
Pulley 41/(5) 35
Tension clamp screw 606 48
Travel 45a 36
Wiper 41/(6), 44o,60c(2) 35,36,48
Technical characteristics 4 1
Tension :
Arm 606(2) 48
Pulley 606(1) 48
Theory of operation, condensed 45a 36
Tools, parts, and sets supplied 39 33
Transformer :
Input 45a 36
Output 45a 36
Trouble :
Location, general ' 55 44
Shooting chart 59 46
True zero 24 17
Unusual conditions 28 24
Use of speed number 32d 28
Voltage :
And resistance measurements 58 45
Doubler 50a 41
Extinction 496 41
Heater 50(1 41
Ignition 496 41
I'lutc £uid screen ■- * • 50ti 41
Volume control 20a, 32a (4) , 466 14, 25, 37
Weatherproofing, general 42a 35
Winter maintenance 426 35
Wire-line method 35a 30
Zero counter reading 24 17
<T U. 8. GOVERNMENT PRINTING OFFICE: I95I-949392
I
